Patent Publication Number: US-2021192565-A1

Title: Methods and apparatus to correct misattributions of media impressions

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/146,912, filed on Sep. 28, 2018, which is a continuation of U.S. patent application Ser. No. 14/528,495, filed Oct. 30, 2014, which claims the benefit of, and priority from, U.S. Provisional Patent Application Ser. No. 61/923,959 filed on Jan. 6, 2014, all of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to monitoring media and, more particularly, to methods and apparatus to correct misattributions of media impressions. 
     BACKGROUND 
     Traditionally, audience measurement entities determine audience engagement levels for media based on registered panel members. That is, an audience measurement entity enrolls people who consent to being monitored into a panel. The audience measurement entity then monitors those panel members to determine media (e.g., television programs or radio programs, movies, DVDs, advertisements, streaming media, websites, etc.) exposed to those panel members. In this manner, the audience measurement entity can determine exposure metrics for different media based on the collected media measurement data. 
     Techniques for monitoring user access to Internet resources such as web pages, advertisements and/or other Internet-accessible media have evolved significantly over the years. Some known systems perform such monitoring primarily through server logs. In particular, entities serving media on the Internet can use known techniques to log the number of requests received for their media (e.g., content and/or advertisements) at their server. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example client device that reports audience impressions for media to impression collection entities to facilitate identifying total impressions and sizes of unique audiences exposed to different media. 
         FIG. 2  is an example communication flow diagram of an example manner in which an audience measurement entity (AME) and a database proprietor (DP) can collect impressions and demographic information based on a client device reporting impressions to the AME and the DP. 
         FIG. 3  illustrates example impressions collected by the AME and example impressions collected by the DP with a misattribution error. 
         FIG. 4  illustrates example audience adjustment (AA) factors for unique audience sizes of different demographic groups determined based on the example impressions of  FIG. 3 . 
         FIG. 5  illustrates example impression adjustment (IA) factors for total impressions of different demographic groups determined based on the example impressions of  FIG. 3 . 
         FIG. 6  illustrates example misattribution-corrected unique audience values and example misattribution-corrected impression counts determined based on the example AA factors of  FIG. 4  and the example IA factors of  FIG. 5  for different demographic groups. 
         FIG. 7  illustrates example misattribution-corrected unique audience values and example misattribution-corrected impression counts determined based on the example IA factors of  FIG. 5  and example impression frequencies for different demographic groups. 
         FIG. 8  is a flow diagram representative of example machine readable instructions that may be executed to implement the misattribution corrector of  FIG. 2  to determine misattribution-corrected unique audience sizes and misattribution-corrected impression counts. 
         FIG. 9  illustrates an example processor system structured to execute the example instructions of  FIG. 8  to implement the example AME of  FIGS. 1 and/or 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Techniques for monitoring user access to Internet-accessible media such as web pages, advertisements, content and/or other media have evolved significantly over the years. At one point in the past, such monitoring was done primarily through server logs. In particular, entities serving media on the Internet would log the number of requests received for their media at their server. Basing Internet usage research on server logs is problematic for several reasons. For example, server logs can be tampered with either directly or via zombie programs which repeatedly request media from the server to increase the server log counts. Secondly, media is sometimes retrieved once, cached locally and then repeatedly viewed from the local cache without involving the server in the repeat viewings. Server logs cannot track these repeat views of cached media. Thus, server logs are susceptible to both over-counting and under-counting errors. 
     The inventions disclosed in Blumenau, U.S. Pat. No. 6,108,637, fundamentally changed the way Internet monitoring is performed and overcame the limitations of the server side log monitoring techniques described above. For example, Blumenau disclosed a technique wherein Internet media to be tracked is tagged with beacon instructions. In particular, monitoring instructions are associated with the hypertext markup language (HTML) of the media to be tracked. When a client requests the media, both the media and the beacon instructions are downloaded to the client. The beacon instructions are, thus, executed whenever the media is accessed, be it from a server or from a cache. 
     The beacon instructions cause monitoring data reflecting information about the access to the media to be sent from the client that downloaded the media to a monitoring entity. Typically, the monitoring entity is an audience measurement entity (AME) that did not provide the media to the client and who is a trusted (e.g., neutral) third party for providing accurate usage statistics (e.g., The Nielsen Company, LLC). Advantageously, because the beaconing instructions are associated with the media and executed by the client browser whenever the media is accessed, the monitoring information is provided to the AME irrespective of whether the client is a panelist of the AME. 
     Audience measurement entities and/or other businesses often desire to link demographics to the monitoring information. To address this issue, the AME establishes a panel of users who have agreed to provide their demographic information and to have their Internet browsing activities monitored. When an individual joins the panel, they provide detailed information concerning their identity and demographics (e.g., gender, age, ethnicity, income, home location, occupation, etc.) to the AME. The audience measurement entity sets a cookie on the panelist computer that enables the audience measurement entity to identify the panelist whenever the panelist accesses tagged media and, thus, sends monitoring information to the audience measurement entity. 
     Since most of the clients providing monitoring information from the tagged media are not panelists and, thus, are unknown to the audience measurement entity, it is necessary to use statistical methods to impute demographic information based on the data collected for panelists to the larger population of users providing data for the tagged media. However, panel sizes of audience measurement entities remain small compared to the general population of users. Thus, a problem is presented as to how to increase panel sizes while ensuring the demographics data of the panel is accurate. 
     There are many database proprietors operating on the Internet. These database proprietors provide services to large numbers of subscribers. In exchange for the provision of the service, the subscribers register with the proprietor. As part of this registration, the subscribers provide detailed demographic information. Examples of such database proprietors include social network providers, email providers, etc. such as Facebook, Myspace, Twitter, Yahoo!, Google, etc. These database proprietors set cookies or other device/user identifiers on the client devices of their subscribers to enable the database proprietor to recognize the user when they visit their website. 
     The protocols of the Internet make cookies inaccessible outside of the domain (e.g., Internet domain, domain name, etc.) on which they were set. Thus, a cookie set, for example, in the amazon.com domain is accessible to servers in the amazon.com domain, but not to servers outside that domain. Therefore, although an audience measurement entity might find it advantageous to access the cookies set by the database proprietors, they are unable to do so. 
     The inventions disclosed in Mainak et al., U.S. Pat. No. 8,370,489, which is incorporated by reference herein in its entirety, enable an audience measurement entity to leverage the existing databases of database proprietors to collect more extensive Internet usage and demographic data by extending the beaconing process to encompass partnered database proprietors and by using such partners as interim data collectors. The inventions disclosed in Mainak et al. accomplish this task by structuring the AME to respond to beacon requests from clients (who may not be a member of an audience member panel and, thus, may be unknown to the audience member entity) and redirect the client from the audience measurement entity to a database proprietor such as a social network site partnered with the audience member entity. The redirection initiates a communication session between the client accessing the tagged media and the database proprietor. The database proprietor (e.g., Facebook) can access any cookie it has set on the client to thereby identify the client based on the internal records of the database proprietor. In the event the client corresponds to a subscriber of the database proprietor, the database proprietor logs an impression in association with the demographics data associated with the client and subsequently forwards logged impressions to the audience measurement company. In the event the client does not correspond to a subscriber of the database proprietor, the database proprietor may redirect the client to the audience measurement entity and/or another database proprietor. The audience measurement entity may respond to the redirection from the first database proprietor by redirecting the client to a second, different database proprietor that is partnered with the audience measurement entity. That second database proprietor may then attempt to identify the client as explained above. This process of redirecting the client from database proprietor to database proprietor can be performed any number of times until the client is identified and the media exposure logged, or until all database proprietor partners have been contacted without a successful identification of the client. The redirections all occur automatically so the user of the client is not involved in the various communication sessions and may not even know they are occurring. 
     Periodically or aperiodically the partnered database proprietors provide their logs and demographic information to the audience measurement entity which then compiles the collected data into statistical reports accurately identifying the demographics of persons accessing the tagged media. Because the identification of clients is done with reference to enormous databases of users far beyond the quantity of persons present in a conventional audience measurement panel, the data developed from this process is extremely accurate, reliable and detailed. 
     Significantly, because the audience measurement entity remains the first leg of the data collection process (e.g., receives the request generated by the beacon instructions from the client), the audience measurement entity is able to obscure the source of the media access being logged as well as the identity of the media itself from the database proprietors (thereby protecting the privacy of the media sources), without compromising the ability of the database proprietors to log impressions for their subscribers. Further, when cookies are used as device/user identifiers, the Internet security cookie protocols are complied with because the only servers that access a given cookie are associated with the Internet domain (e.g., Facebook.com) that set that cookie. 
     Examples disclosed in Mainak et al. (U.S. Pat. No. 8,370,489) can be used to determine any type of media impressions or exposures (e.g., content impressions, advertisement impressions, content exposure, and/or advertisement exposure) using demographic information, which is distributed across different databases (e.g., different website owners, service providers, etc.) on the Internet. Not only do such disclosed examples enable more accurate correlation of Internet advertisement exposure to demographics, but they also effectively extend panel sizes and compositions beyond persons participating in the panel of an audience measurement entity and/or a ratings entity to persons registered in other Internet databases such as the databases of social media sites such as Facebook, Twitter, Google, etc. Such extension effectively leverages the media tagging capabilities of the ratings entity and the use of databases of non-ratings entities such as social media and other websites to create an enormous, demographically accurate panel that results in accurate, reliable measurements of exposures to Internet media such as advertising and/or programming. 
     In illustrated examples disclosed herein, media exposure is measured in terms of online Gross Rating Points. A Gross Rating Point (GRP) is a unit of measurement of audience size that has traditionally been used in the television ratings context. It is used to measure exposure to one or more media (e.g., programs, advertisements, etc.) without regard to multiple exposures of the same media to individuals. In terms of television (TV) advertisements, one GRP is equal to 1% of TV households. While GRPs have traditionally been used as a measure of television viewership, examples disclosed herein may be used in connection with generating online GRPs for online media to provide a standardized metric that can be used across the Internet to accurately reflect online advertisement exposure. Such standardized online GRP measurements can provide greater certainty to advertisers that their online advertisement money is well spent. It can also facilitate cross-medium comparisons such as viewership of TV advertisements and online advertisements, exposure to radio advertisements and online media, etc. Because examples disclosed herein may be used to correct impressions that associate exposure measurements with corresponding demographics of users, the information processed using examples disclosed herein may also be used by advertisers to more accurately identify markets reached by their advertisements and/or to target particular markets with future advertisements. 
     Traditionally, audience measurement entities (also referred to herein as “ratings entities”) determine demographic reach for advertising and media programming based on registered panel members. That is, an audience measurement entity enrolls people that consent to being monitored into a panel. During enrollment, the audience measurement entity receives demographic information from the enrolling people so that subsequent correlations may be made between advertisement/media exposures to those panelists and different demographic markets. Unlike traditional techniques in which audience measurement entities rely solely on their own panel member data to collect demographics-based audience measurements, example methods, apparatus, and/or articles of manufacture disclosed herein enable an audience measurement entity to share demographic information with other entities that operate based on user registration models. As used herein, a user registration model is a model in which users subscribe to services of those entities by creating an account and providing demographic-related information about themselves. Sharing of demographic information associated with registered users of database proprietors enables an audience measurement entity to extend or supplement their panel data with substantially reliable demographics information from external sources (e.g., database proprietors), thus extending the coverage, accuracy, and/or completeness of the AMA&#39;s demographics-based audience measurements. Such access also enables the audience measurement entity to monitor persons who would not otherwise have joined an audience measurement panel. Any entity having a network-accessible database identifying demographics of a set of individuals may cooperate with the audience measurement entity. Such entities may be referred to as “database proprietors” and include entities such as Facebook, Google, Yahoo!, MSN, Twitter, Apple iTunes, Experian, etc. 
     To increase the likelihood that measured viewership is accurately attributed to the correct demographics, examples disclosed herein use demographic information located in the audience measurement entity&#39;s records as well as demographic information located at one or more database proprietors that maintain records or profiles of users having accounts therewith. In this manner, examples disclosed herein may be used to supplement demographic information maintained by a ratings entity (e.g., an AME such as The Nielsen Company of Schaumburg, Ill., United States of America, that collects media exposure measurements and/or demographics) with demographic information from one or more different database proprietors. 
     The use of demographic information from disparate data sources (e.g., high-quality demographic information from the panels of an audience measurement company and/or registered user data of web service providers) results in improved reporting effectiveness of metrics for both online and offline advertising campaigns. Example techniques disclosed herein use online registration data to identify demographics of users and use server impression counts, tagging (also referred to herein as beaconing), and/or other techniques to track quantities of impressions attributable to those users. Online web service providers such as social networking sites (e.g., Facebook) and multi-service providers (e.g., Yahoo!, Google, Experian, etc.) (collectively and individually referred to herein as database proprietors) maintain detailed demographic information (e.g., age, gender, geographic location, race, income level, education level, religion, etc.) collected via user registration processes. As used herein, an impression is defined to be an event in which a home or individual is exposed to corresponding media (e.g., content and/or an advertisement). Thus, an impression represents a home or an individual having been exposed to media (e.g., an advertisement, content, a group of advertisements, and/or a collection of content). In Internet advertising, a quantity of impressions or impression count is the total number of times media (e.g., content, an advertisement or advertisement campaign) has been accessed by a web population (e.g., the number of times the media is accessed). As used herein, a demographic impression is defined to be an impression that is associated with a characteristic (e.g., a demographic characteristic) of the person exposed to the media. 
     Although such techniques for collecting media impressions are based on highly accurate demographic information, in some instances collected impressions may be misattributed to the wrong person and, thus, associated with incorrect demographic information. For example, in a household having multiple people that use the same client device (e.g., the same computer, tablet, smart internet appliance, etc.), collected impressions from that client device may be misattributed to a member of the household that is not the current user of the client device. That is, when an online user visits a website and is exposed to an advertisement on that site that has been tagged with beacon instructions, there is a redirect to a server of a database proprietor (e.g., Facebook, Yahoo, Google, etc.). The database proprietor then looks into a most recent cookie set by the database proprietor in the web browser of that client device. The database proprietor then attributes the impression to the user account corresponding to the cookie value. For example, the cookie value is one that was previously set in the client device by the database proprietor to correspond to a particular registered user account of the person that used the client device to most recently log into the website of that database proprietor. After collecting and attributing the impression to the user account associated with the retrieved cookie value, the database proprietor aggregates the total collected impressions and the size of the unique audience based on demographics associated with user accounts for all logged impressions. When this occurs over time and across many households, a number of collected impressions are misattributed to the wrong demographic information because some people use client devices after another person (e.g., another household member) has logged into a user account registered with the database proprietor without logging themselves (e.g., the current audience member) in. As such, a cookie corresponding to the previous person is still accessed from the client device while the subsequent user of the client device (e.g., a user that did not log into a corresponding user account registered with the database proprietor) accesses media on the client device which causes impressions to be misattributed to the previous person associated with the accessed cookie. 
     As used herein, a unique audience measure is based on audience members distinguishable from one another. That is, a particular audience member exposed to particular media is measured as a single unique audience member regardless of how many times that audience member is exposed to that particular media. If that particular audience member is exposed multiple times to the same media, the multiple exposures for the particular audience member to the same media is counted as only a single unique audience member. In this manner, impression performance for particular media is not disproportionately represented when a small subset of one or more audience members is exposed to the same media an excessively large number of times while a larger number of audience members is exposed fewer times or not at all to that same media. By tracking exposures to unique audience members, a unique audience measure may be used to determine a reach measure to identify how many unique audience members are reached by media. In some examples, increasing unique audience and, thus, reach, is useful for advertisers wishing to reach a larger audience base. 
     As used herein, total impressions refers to the total number of collected impressions for particular media regardless of whether multiple ones of those impressions are attributable to the same audience members. That is, multiple impressions accounted for in the total impressions may be attributable to a same audience member. 
     Misattribution is a measurement error that typically arises when impressions are collected from a same client device that is shared by multiple people in that a media impression caused by one person that is currently using the client device is incorrectly attributed (i.e., misattributed) to another person that previously used the same client device. Sharing of a client device can occur between two individuals who: (1) live in the same household, and/or (2) have access to the same client device. Misattribution occurs when, for a particular media exposure on a client device, a logged-in-user of a database proprietor service (e.g., Facebook) is not the same as the current user of the client device that is being exposed to the media. For example, if person A logs into the database proprietor&#39;s website in the morning on a client device, but person B uses the same client device in the afternoon without logging in (e.g., without user A logging out) and is exposed to media tagged with beacon instructions, the database proprietor attributes the impression to person A since he/she was the last person to log into the database proprietor&#39;s site from that client device, while actually it was person B who was using the client device when the media was presented. 
     Examples disclosed herein can be used to correct misattribution in collected impressions by applying a misattribution correction to impression data obtained from a database proprietor (e.g., Facebook, Yahoo, Google, etc.) after a profile correction (e.g., a Decision Tree (DT) model) has been applied to the impression data. Examples disclosed herein may be implemented by an audience measurement entity (e.g., any entity interested in measuring or tracking audience exposures to advertisements, content, and/or any other media) in cooperation with any number of database proprietors such as online web services providers. Such database proprietors/online web services providers may be social network sites (e.g., Facebook, Twitter, MySpace, etc.), multi-service sites (e.g., Yahoo!, Google, Axiom, Catalina, etc.), online retailer sites (e.g., Amazon.com, Buy.com, etc.), credit reporting sites (e.g., Experian), and/or any other web service(s) site that maintains user registration records. 
     Example methods and/or articles of manufacture comprising computer readable instructions disclosed herein may be used to receive, at a first internet domain, a first request from a client device, the first request indicative of access to media at the client device. In such examples, a response is sent from the first internet domain to the client device. In such examples, the response instructs the client device to send a second request to a second internet domain. In such examples, the second request is to be indicative of the access to the media at the client device. In such examples, an impressions adjustment factor is determined for a first demographic group based on first impressions reported by the client device to the first internet domain and second impressions reported by the client device to the second internet domain. In such example, the first and second impressions correspond to the same media accessed on the client device. In such examples, a misattribution-corrected impressions count is determined for the first demographic group based on the impressions adjustment factor and based on a second impressions count determined at the second internet domain for the first demographic group. In such examples, the second impressions count includes an error based on some of the second impressions being misattributed at the second internet domain to the first demographic group when the some of the second impressions correspond to a second demographic group. 
     In some examples, determining the misattribution-corrected impression count involves shifting an impression from the second impressions count corresponding to the first demographic group to a third impressions count corresponding to the second demographic group based on the impressions adjustment factor. In some examples, the first impressions are reported by the client device to an audience measurement entity at the first internet domain that does not provide the media to the client device, and a user of the client device is a panel member of the audience measurement entity. In some examples, the second impressions are reported by the client device to a social network service at the second internet domain to which a user of the client device is subscribed. In some examples, the impressions adjustment factor is to correct impression quantities having inaccuracies due to impressions incorrectly attributed to demographic data not corresponding to persons corresponding to the impressions. 
     In some examples, determining the impressions adjustment factor involves subtracting a first unique audience size determined by an audience measurement entity at the first internet domain based on the first impressions from a second unique audience size determined by a database proprietor at the second internet domain based on the second impressions to generate a difference. In such examples, the difference is divided by a total impressions count of the first impressions to determine the impressions adjustment factor. 
     In some examples, the error in the second impressions count is based on an entity at the second internet domain incorrectly identifying a user of the client device as belonging to the first demographic group when the user belongs to the second demographic group. In such examples, the misattribution-corrected impressions count comprises fewer impressions than the second impression count based on shifting an impression corresponding to the user from the second impressions count corresponding to the first demographic group to a third impressions count corresponding to the second demographic group based on the impressions adjustment factor. 
     In some examples, the misattribution-corrected impressions count is determined based on the impressions adjustment factor without communicating with individual online users about their online media access activities and without using survey responses from the online users to determine the error. In some examples, network communication bandwidth is conserved by not communicating with individual online users about their online media access activities and by not requesting survey responses from the online users to determine the error. In some examples, computer processing resources are conserved by not communicating with individual online users about their online media access activities and by not requesting survey responses from the online users to determine the error. 
     Example disclosed apparatus include an example impression collector to receive, at a first internet domain, a first request from a client device, the first request indicative of access to media at the client device. The example impression collector is also to send, from the first internet domain, a response to the client device, the response to instruct the client device to send a second request to a second internet domain, the second request to be indicative of the access to the media at the client device. Such example apparatus also include an impressions adjustment factor determiner to determine an impressions adjustment factor for a first demographic group based on first impressions reported by the client device to the first internet domain and second impressions reported by the client device to the second internet domain. In such examples, the first and second impressions correspond to the same media accessed on the client device. Such example apparatus also includes an impressions corrector to determine a misattribution-corrected impressions count for the first demographic group based on the impressions adjustment factor and based on a second impressions count determined at the second internet domain for the first demographic group. In such examples, the second impressions count includes an error based on some of the second impressions being misattributed at the second internet domain to the first demographic group when the some of the second impressions correspond to a second demographic group. 
     In some examples, the impressions corrector is to determine the misattribution-corrected impressions count by shifting an impression from the second impressions count corresponding to the first demographic group to a third impressions count corresponding to the second demographic group based on the impressions adjustment factor. In some examples, the first impressions are reported by the client device to an audience measurement entity at the first internet domain that does not provide the media to the client device. In some examples, a user of the client device is a panel member of the audience measurement entity. In some examples, the second impressions are reported by the client device to a social network service at the second internet domain to which a user of the client device is subscribed. 
     In some examples, the impressions adjustment factor determiner is to determine the impressions adjustment factor by subtracting a first unique audience size determined by an audience measurement entity at the first internet domain based on the first impressions from a second unique audience size determined by a database proprietor at the second internet domain based on the second impressions to generate a difference. In such examples, the difference is divided by a total impressions count of the first impressions. 
     In some examples, the impressions adjustment factor is to correct impression quantities having inaccuracies due to impressions incorrectly attributed to demographic data not corresponding to persons corresponding to the impressions. In some examples, the error in the second impressions count is based on an entity at the second internet domain incorrectly identifying a user of the client device as belonging to the first demographic group when the user belongs to the second demographic group. In some examples, the misattribution-corrected impressions count include fewer impressions than the second impression count based on shifting an impression corresponding to the user from the second impressions count corresponding to the first demographic group to a third impressions count corresponding to the second demographic group based on the impressions adjustment factor. 
     In some examples, the impressions corrector determines the misattribution-corrected impressions based on the impressions adjustment factor without communicating with individual online users about their online media access activities and without using survey responses from the online users to determine the error. In some examples, by determining the misattribution-corrected impressions using the impressions corrector, network communication bandwidth is conserved by not communicating with individual online users about their online media access activities and by not requesting survey responses from the online users to determine the error. In some examples, by determining the misattribution-corrected impressions using the impressions corrector, computer processing resources are conserved by not communicating with individual online users about their online media access activities and by not requesting survey responses from the online users to determine the error. 
     Example methods and/or articles of manufacture comprising computer readable instructions disclosed herein may be used to receive, at a first internet domain, a first request from a client device, the first request indicative of access to media at the client device. In such examples, a response is sent from the first internet domain to the client device. In such examples, the response is to instruct the client device to send a second request to a second internet domain. In such examples, the second request is to be indicative of the access to the media at the client device. In such examples, an audience adjustment factor is determined for a demographic group based on first impressions reported by the client device to the first internet domain and second impressions reported by the client device to the second internet domain. In such examples, the first and second impressions correspond to the same media accessed on the client device. In such examples, a misattribution-corrected unique audience size is determined for the demographic group based on the audience adjustment factor and based on a second unique audience size determined at the second internet domain for the demographic group. In such examples, the second unique audience size includes an error based on third impressions misattributed at the second internet domain to the demographic group when the third impressions correspond to another demographic group. 
     In some examples, determining the audience adjustment factor involves dividing a third unique audience size corresponding to the first impressions by a fourth unique audience size corresponding to the second impressions. In some examples, determining the misattribution-corrected unique audience size for the demographic group involves dividing the second unique audience size by the audience adjustment factor. In some examples, the first impressions are reported by the client device to an audience measurement entity at the first internet domain that does not provide the media to the client device, and a user of the client device is a panel member of the audience measurement entity. In some examples, the second impressions are reported by the client device to a social network service at the second internet domain to which a user of the client device is subscribed. In some examples, the audience adjustment factor is to correct unique audience size values having inaccuracies due to impressions incorrectly attributed to demographic data not corresponding to persons corresponding to the impressions. 
     In some examples, the error in the second unique audience size is based on an entity at the second internet domain incorrectly identifying a user of the client device as belonging to the demographic group when the user belongs to the another demographic group. In some such examples, the misattribution-corrected unique audience size is different than the second unique audience size based on dividing the second unique audience size by the audience adjustment factor. 
     In some examples, the misattribution-corrected unique audience size is determined based on the audience adjustment factor without communicating with individual online users about their online media access habits and without using survey responses from the online users to determine the error. In some examples, network communication bandwidth is conserved by not communicating with individual online users about their online media access habits and by not requesting survey responses from the online users to determine the error. In some examples, computer processing resources are conserved by not communicating with individual online users about their online media access habits and by not requesting survey responses from the online users to determine the error. 
     Example disclosed apparatus include an example impression collector to receive, at a first internet domain, a first request from a client device. In such examples, the first request is indicative of access to media at the client device. The example impression collector is also to send, from the first internet domain, a response to the client device. In such examples, the response is to instruct the client device to send a second request to a second internet domain. In such examples, the second request is to be indicative of the access to the media at the client device. Such example apparatus also include an audience adjustment factor determiner to determine an audience adjustment factor for a demographic group based on first impressions reported by the client device to the first internet domain and second impressions reported by the client device to the second internet domain. In such examples, the first and second impressions correspond to the same media accessed on the client device. Such example apparatus also include a unique audience corrector to determine a misattribution-corrected unique audience size for the demographic group based on the audience adjustment factor and based on a second unique audience size determined at the second internet domain for the demographic group. In such examples, the second unique audience size includes an error based on third impressions misattributed at the second internet domain to the demographic group when the third impressions correspond to another demographic group. 
     In some examples, the audience adjustment factor determiner is to determine the audience adjustment factor by dividing a third unique audience size corresponding to the first impressions by a fourth unique audience size corresponding to the second impressions. In some examples, the unique audience corrector is to determine the misattribution-corrected unique audience size for the demographic group by dividing the second unique audience size by the audience adjustment factor. In some examples, the first impressions are reported by the client device to an audience measurement entity at the first internet domain that does not provide the media to the client device, and a user of the client device is a panel member of the audience measurement entity. In some examples, the second impressions are reported by the client device to a social network service at the second internet domain to which a user of the client device is subscribed. In some examples, the audience adjustment factor is to correct unique audience size values having inaccuracies due to impressions incorrectly attributed to demographic data not corresponding to persons corresponding to the impressions. 
     In some examples, the error in the second unique audience size is based on an entity at the second internet domain incorrectly identifying a user of the client device as belonging to the demographic group when the user belongs to the another demographic group. In some such examples, the misattribution-corrected unique audience size comprising dividing the second unique audience size by the audience adjustment factor. 
     In some examples, the unique audience corrector is to determine the misattribution-corrected unique audience size based on the audience adjustment factor without communicating with individual online users about their online media access habits and without using survey responses from the online users to determine the error. In some examples, by determining the misattribution-corrected unique audience size, the unique audience corrector conserves network communication bandwidth by not communicating with individual online users about their online media access habits and by not requesting survey responses from the online users to determine the error. In some examples, by determining the misattribution-corrected unique audience size, the unique audience corrector conserves computer processing resources by not communicating with individual online users about their online media access habits and by not requesting survey responses from the online users to determine the error. 
       FIG. 1  illustrates an example client device  102  that reports audience impressions for media to impression collection entities  104  to facilitate identifying total impressions and sizes of unique audiences exposed to different media. As used herein, the term impression collection entity refers to any entity that collects impression data. The client device  102  of the illustrated example may be any device capable of accessing media over a network. For example, the client device  102  may be a computer, a tablet, a mobile device, a smart television, or any other Internet-capable device or appliance. Examples disclosed herein may be used to collect impression information for any type of media including content and/or advertisements. Media may include advertising and/or content such as web pages, streaming video, streaming audio, movies, and/or any other type of content and/or advertisement deliver via satellite, broadcast, cable television, radio frequency (RF) terrestrial broadcast, Internet (e.g., internet protocol television (IPTV)), television broadcasts, radio broadcasts and/or any other vehicle for delivering media. In some examples, media includes user-generated media that is, for example, uploaded to media upload sites such as YouTube and subsequently downloaded and/or streamed by one or more client devices for playback. Media may also include advertisements. Advertisements are typically distributed with content (e.g., programming). Traditionally, content is provided at little or no cost to the audience because it is subsidized by advertisers that pay to have their advertisements distributed with the content. As used herein, “media” refers collectively and/or individually to content and/or advertisement(s) of any type(s). 
     In the illustrated example, the client device  102  employs a web browser and/or applications (e.g., apps) to access media, some of which include instructions that cause the client device  102  to report media monitoring information to one or more of the impression collection entities  104 . That is, when the client device  102  of the illustrated example accesses media, a web browser and/or application of the client device  102  executes instructions in the media to send a beacon request or impression request  108  to one or more of the impression collection entities  104  via, for example, the Internet  110 . The beacon requests  108  of the illustrated example include information about accesses to media at the client device  102 . Such beacon requests  108  allow monitoring entities, such as the impression collection entities  104 , to collect impressions for different media accessed via the client device  102 . In this manner, the impression collection entities  104  can generate large impression quantities for different media (e.g., different content and/or advertisement campaigns). 
     The impression collection entities  104  of the illustrated example include an example audience measurement entity (AME)  114  and an example database proprietor (DP)  116 . In the illustrated example, the AME  114  does not provide the media to the client device  102  and is a trusted (e.g., neutral) third party (e.g., The Nielsen Company, LLC) for providing accurate media access statistics. In the illustrated example, the database proprietor  116  is one of many database proprietors that operates on the Internet to provide services to large numbers of subscribers. Such services may be email services, social networking services, news media services, cloud storage services, streaming music services, streaming video services, online retail shopping services, credit monitoring services, etc. Example database proprietors include social network sites (e.g., Facebook, Twitter, MySpace, etc.), multi-service sites (e.g., Yahoo!, Google, etc.), online retailer sites (e.g., Amazon.com, Buy.com, etc.), credit reporting services (e.g., Experian) and/or any other web service(s) site that maintains user registration records. In examples disclosed herein, the database proprietor  116  maintains user account records corresponding to users registered for Internet-based services provided by the database proprietors. That is, in exchange for the provision of services, subscribers register with the database proprietor  116 . As part of this registration, the subscribers provide detailed demographic information to the database proprietor  116 . Demographic information may include, for example, gender, age, ethnicity, income, home location, education level, occupation, etc. In the illustrated example, the database proprietor  116  sets a device/user identifier (e.g., an identifier described below in connection with  FIG. 2 ) on a subscriber&#39;s client device  102  that enables the database proprietor  116  to identify the subscriber. 
     In the illustrated example, when the database proprietor  116  receives a beacon/impression request  108  from the client device  102 , the database proprietor  116  requests the client device  102  to provide the device/user identifier that the database proprietor  116  had previously set for the client device  102 . The database proprietor  116  uses the device/user identifier corresponding to the client device  102  to identify demographic information in its user account records corresponding to the subscriber of the client device  102 . In this manner, the database proprietor  116  can generate demographic impressions by associating demographic information with an audience impression for the media accessed at the client device  102 . As explained above, a demographic impression is an impression that is associated with a characteristic (e.g., a demographic characteristic) of the person exposed to the media. 
     In the illustrated example, the AME  114  establishes an AME panel of users who have agreed to provide their demographic information and to have their Internet browsing activities monitored. When an individual joins the AME panel, the person provides detailed information concerning the person&#39;s identity and demographics (e.g., gender, age, ethnicity, income, home location, occupation, etc.) to the AME  114 . The AME  114  sets a device/user identifier (e.g., an identifier described below in connection with  FIG. 2 ) on the person&#39;s client device  102  that enables the AME  114  to identify the panelist. An AME panel may be a cross-platform home television/computer (TVPC) panel built and maintained by the AME  114 . In other examples, the AME panel may be a computer panel or internet-device panel without corresponding to a television audience panel. In yet other examples, the AME panel may be a cross-platform radio/computer panel and/or a panel formed for other mediums. 
     In the illustrated example, when the AME  114  receives a beacon request  108  from the client device  102 , the AME  114  requests the client device  102  to provide the AME  114  with the device/user identifier that the AME  114  previously set in the client device  102 . The AME  114  uses the device/user identifier corresponding to the client device  102  to identify demographic information in its user AME panelist records corresponding to the panelist of the client device  102 . In this manner, the AME  114  can generate demographic impressions by associating demographic information with an audience impression for the media accessed at the client device  102 . 
     In the illustrated example, the client device  102  is used in an example household  120  in which household members  122  and  124  (identified as subscriber A  122  and subscriber B  124 ) are subscribers of an internet-based service offered by the database proprietor  116 . In the illustrated example, subscriber A  122  and subscriber B  124  share the client device  102  to access the internet-based service of the database proprietor  116  and to access other media via the Internet  110 . In the illustrated example, when the database proprietor  116  receives a beacon/impression request  108  for media accessed via the client device  102 , the database proprietor  116  logs an impression for the media access as corresponding to the subscriber  122 ,  124  of the household  120  that most recently logged into the database proprietor  116 . Misattributions of impressions logged by the database proprietor  116  are likely to occur in circumstances similar to the example household  120  of  FIG. 1  in which multiple people in a household share a client device. For example, if the subscriber A  122  logs into a service of the database proprietor  116  on the client device  102 , and the subscriber B  124  subsequently uses the client device  102  without logging in to the service of the database proprietor  116 , the database proprietor  116  attributes logged impression to the subscriber A  122  even though the use is actually by subscriber B  124  because the subscriber A  122  was the last person to log into the database proprietor  116  and, thus, the subscriber A  122  was most recently identified by the database proprietor  116  as the subscriber using the client device  102 . As such, even though the subscriber B  124  was subsequently using the client device  102 , impressions logged by the database proprietor  116  during such use are not attributed to the correct person (i.e., the subscriber B  124 ) because the most recent login detected by the database proprietor  116  corresponded to the subscriber A  122 . In the illustrated example, logins are used by the database proprietor  116  to identify subscribers using particular devices by associating device/user identifiers on the client devices with subscriber accounts at the database proprietor  116  corresponding to usernames used during the logins. As such, the database proprietor  116  assumes that the most recent login is indicative of a subscriber using the client device  102  until another login event is received at the database proprietor  116  that identifies a different subscriber. Such assumptions based on the most recent login lead to the above-described misattributions. 
       FIG. 2  illustrates an example communication flow diagram of an example manner in which the AME  114  and the database proprietor  116  of  FIG. 1  can collect impressions and demographic information based on the client device  102  reporting impressions to the AME  114  and the database proprietor  116 .  FIG. 2  also shows an example misattribution corrector  202 . The misattribution corrector  202  of the illustrated example is to correct unique audience sizes and impression counts that are based on impressions reported by client devices (e.g., the client device  102 ) and for which the database proprietor  116  has misattributed some of those impressions to incorrect people and, thus, incorrect demographic information. The example chain of events shown in  FIG. 2  occurs when the client device  102  accesses media for which the client device  102  reports an impression to the AME  114  and the database proprietor  116 . In some examples, the client device  102  reports impressions for accessed media based on instructions (e.g., beacon instructions) embedded in the media that instruct the client device  102  (e.g., instruct a web browser or an app in the client device  102 ) to send beacon/impression requests (e.g., the beacon/impression requests  108  of  FIG. 1 ) to the AME  114  and/or the database proprietor  116 . In such examples, the media having the beacon instructions is referred to as tagged media. In other examples, the client device  102  reports impressions for accessed media based on instructions embedded in apps or web browsers that execute on the client device  102  to send beacon/impression requests (e.g., the beacon/impression requests  108  of  FIG. 1 ) to the AME  114 , and/or the database proprietor  116  for corresponding media accessed via those apps or web browsers. In any case, the beacon/impression requests (e.g., the beacon/impression requests  108  of  FIG. 1 ) include device/user identifiers (e.g., AME IDs and/or DP IDs) as described further below to allow the corresponding AME  114  and/or database proprietor  116  to associate demographic information with resulting logged impressions. 
     In the illustrated example, the client device  102  accesses media  206  that is tagged with beacon instructions  208 . The beacon instructions  208  cause the client device  102  to send a beacon/impression request  212  to an AME impressions collector  218  when the client device  102  accesses the media  206 . For example, a web browser and/or app of the client device  102  executes the beacon instructions  208  in the media  206  which instruct the browser and/or app to generate and send the beacon/impression request  212 . In the illustrated example, the client device  102  sends the beacon/impression request  212  to the AME impression collector  218  using an HTTP (hypertext transfer protocol) request addressed to the URL (uniform resource locator) of the AME impressions collector  218  at, for example, a first internet domain of the AME  114 . The beacon/impression request  212  of the illustrated example includes a media identifier  213  (e.g., an identifier that can be used to identify content, an advertisement, and/or any other media) corresponding to the media  206 . In some examples, the beacon/impression request  212  also includes a site identifier (e.g., a URL) of the website that served the media  206  to the client device  102  and/or a host website ID (e.g., www.acme.com) of the website that displays or presents the media  206 . In the illustrated example, the beacon/impression request  212  includes a device/user identifier  214 . In the illustrated example, the device/user identifier  214  that the client device  102  provides in the beacon impression request  212  is an AME ID because it corresponds to an identifier that the AME  114  uses to identify a panelist corresponding to the client device  102 . In other examples, the client device  102  may not send the device/user identifier  214  until the client device  102  receives a request for the same from a server of the AME  114  (e.g., in response to, for example, the AME impressions collector  218  receiving the beacon/impression request  212 ). 
     In some examples, the device/user identifier  214  may be a device identifier (e.g., an international mobile equipment identity (IMEI), a mobile equipment identifier (MEID), a media access control (MAC) address, etc.), a web browser unique identifier (e.g., a cookie), a user identifier (e.g., a user name, a login ID, etc.), an Adobe Flash® client identifier, identification information stored in an HTML5 datastore, and/or any other identifier that the AME  114  stores in association with demographic information about users of the client devices  102 . When the AME  114  receives the device/user identifier  214 , the AME  114  can obtain demographic information corresponding to a user of the client device  102  based on the device/user identifier  214  that the AME  114  receives from the client device  102 . In some examples, the device/user identifier  214  may be encrypted (e.g., hashed) at the client device  102  so that only an intended final recipient of the device/user identifier  214  can decrypt the hashed identifier  214 . For example, if the device/user identifier  214  is a cookie that is set in the client device  102  by the AME  114 , the device/user identifier  214  can be hashed so that only the AME  114  can decrypt the device/user identifier  214 . If the device/user identifier  214  is an IMEI number, the client device  102  can hash the device/user identifier  214  so that only a wireless carrier (e.g., the database proprietor  116 ) can decrypt the hashed identifier  214  to recover the IMEI for use in accessing demographic information corresponding to the user of the client device  102 . By hashing the device/user identifier  214 , an intermediate party (e.g., an intermediate server or entity on the Internet) receiving the beacon request cannot directly identify a user of the client device  102 . 
     In response to receiving the beacon/impression request  212 , the AME impressions collector  218  logs an impression for the media  206  by storing the media identifier  213  contained in the beacon/impression request  212 . In the illustrated example of  FIG. 2 , the AME impressions collector  218  also uses the device/user identifier  214  in the beacon/impression request  212  to identify AME panelist demographic information corresponding to a panelist of the client device  102 . That is, the device/user identifier  214  matches a user ID of a panelist member (e.g., a panelist corresponding to a panelist profile maintained and/or stored by the AME  114 ). In this manner, the AME impressions collector  218  can associate the logged impression with demographic information of a panelist corresponding to the client device  102 . 
     In some examples, the beacon/impression request  212  may not include the device/user identifier  214  if, for example, the user of the client device  102  is not an AME panelist. In such examples, the AME impressions collector  218  logs impressions regardless of whether the client device  102  provides the device/user identifier  214  in the beacon/impression request  212  (or in response to a request for the identifier  214 ). When the client device  102  does not provide the device/user identifier  214 , the AME impressions collector  218  will still benefit from logging an impression for the media  206  even though it will not have corresponding demographics. For example, the AME  114  may still use the logged impression to generate a total impressions count and/or a frequency of impressions (e.g., an impressions frequency) for the media  206 . Additionally or alternatively, the AME  114  may obtain demographics information from the database proprietor  116  for the logged impression if the client device  102  corresponds to a subscriber of the database proprietor  116 . 
     In the illustrated example of  FIG. 2 , to compare or supplement panelist demographics (e.g., for accuracy or completeness) of the AME  114  with demographics from one or more database proprietors (e.g., the database proprietor  116 ), the AME impressions collector  218  returns a beacon response message  222  (e.g., a first beacon response) to the client device  102  including an HTTP “302 Found” re-direct message and a URL of a participating database proprietor  116  at, for example, a second internet domain. In the illustrated example, the HTTP “302 Found” re-direct message in the beacon response  222  instructs the client device  102  to send a second beacon request  226  to the database proprietor  116 . In other examples, instead of using an HTTP “302 Found” re-direct message, redirects may be implemented using, for example, an iframe source instruction (e.g., &lt;iframe src=“ ”&gt;) or any other instruction that can instruct a client device to send a subsequent beacon request (e.g., the second beacon request  226 ) to a participating database proprietor  116 . In the illustrated example, the AME impressions collector  218  determines the database proprietor  116  specified in the beacon response  222  using a rule and/or any other suitable type of selection criteria or process. In some examples, the AME impressions collector  218  determines a particular database proprietor to which to redirect a beacon request based on, for example, empirical data indicative of which database proprietor is most likely to have demographic data for a user corresponding to the device/user identifier  214 . In some examples, the beacon instructions  208  include a predefined URL of one or more database proprietors to which the client device  102  should send follow up beacon requests  226 . In other examples, the same database proprietor is always identified in the first redirect message (e.g., the beacon response  222 ). 
     In the illustrated example of  FIG. 2 , the beacon/impression request  226  may include a device/user identifier  227  that is a DP ID because it is used by the database proprietor  116  to identify a subscriber of the client device  102  when logging an impression. In some instances (e.g., in which the database proprietor  116  has not yet set a DP ID in the client device  102 ), the beacon/impression request  226  does not include the device/user identifier  227 . In some examples, the DP ID is not sent until the DP requests the same (e.g., in response to the beacon/impression request  226 ). In some examples, the device/user identifier  227  is a device identifier (e.g., an international mobile equipment identity (IMEI), a mobile equipment identifier (MEID), a media access control (MAC) address, etc.), a web browser unique identifier (e.g., a cookie), a user identifier (e.g., a user name, a login ID, etc.), an Adobe Flash® client identifier, identification information stored in an HTML5 datastore, and/or any other identifier that the database proprietor  116  stores in association with demographic information about subscribers corresponding to the client devices  102 . When the database proprietor  116  receives the device/user identifier  227 , the database proprietor  116  can obtain demographic information corresponding to a user of the client device  102  based on the device/user identifier  227  that the database proprietor  116  receives from the client device  102 . In some examples, the device/user identifier  227  may be encrypted (e.g., hashed) at the client device  102  so that only an intended final recipient of the device/user identifier  227  can decrypt the hashed identifier  227 . For example, if the device/user identifier  227  is a cookie that is set in the client device  102  by the database proprietor  116 , the device/user identifier  227  can be hashed so that only the database proprietor  116  can decrypt the device/user identifier  227 . If the device/user identifier  227  is an IMEI number, the client device  102  can hash the device/user identifier  227  so that only a wireless carrier (e.g., the database proprietor  116 ) can decrypt the hashed identifier  227  to recover the IMEI for use in accessing demographic information corresponding to the user of the client device  102 . By hashing the device/user identifier  227 , an intermediate party (e.g., an intermediate server or entity on the Internet) receiving the beacon request cannot directly identify a user of the client device  102 . For example, if the intended final recipient of the device/user identifier  227  is the database proprietor  116 , the AME  114  cannot recover identifier information when the device/user identifier  227  is hashed by the client device  102  for decrypting only by the intended database proprietor  116 . 
     In some examples that use cookies as the device/user identifier  227 , when a user deletes a database proprietor cookie from the client device  102 , the database proprietor  116  sets the same cookie value in the client device  102  the next time the user logs into a service of the database proprietor  116 . In such examples, the cookies used by the database proprietor  116  are registration-based cookies, which facilitate setting the same cookie value after a deletion of the cookie value has occurred on the client device  102 . In this manner, the database proprietor  116  can collect impressions for the client device  102  based on the same cookie value over time to generate unique audience (UA) sizes while eliminating or substantially reducing the likelihood that a single unique person will be counted as two or more separate unique audience members. 
     Although only a single database proprietor  116  is shown in  FIGS. 1 and 2 , the impression reporting/collection process of  FIGS. 1 and 2  may be implemented using multiple database proprietors. In some such examples, the beacon instructions  208  cause the client device  102  to send beacon/impression requests  226  to numerous database proprietors. For example, the beacon instructions  208  may cause the client device  102  to send the beacon/impression requests  226  to the numerous database proprietors in parallel or in daisy chain fashion. In some such examples, the beacon instructions  208  cause the client device  102  to stop sending beacon/impression requests  226  to database proprietors once a database proprietor has recognized the client device  102 . In other examples, the beacon instructions  208  cause the client device  102  to send beacon/impression requests  226  to database proprietors so that multiple database proprietors can recognize the client device  102  and log a corresponding impression. In any case, multiple database proprietors are provided the opportunity to log impressions and provide corresponding demographics information if the user of the client device  102  is a subscriber of services of those database proprietors. 
     In some examples, prior to sending the beacon response  222  to the client device  102 , the AME impressions collector  218  replaces site IDs (e.g., URLs) of media provider(s) that served the media  206  with modified site IDs (e.g., substitute site IDs) which are discernable only by the AME  114  to identify the media provider(s). In some examples, the AME impressions collector  218  may also replace a host website ID (e.g., www.acme.com) with a modified host site ID (e.g., a substitute host site ID) which is discernable only by the AME  114  as corresponding to the host website via which the media  206  is presented. In some examples, the AME impressions collector  218  also replaces the media identifier  213  with a modified media identifier  213  corresponding to the media  206 . In this way, the media provider of the media  206 , the host website that presents the media  206 , and/or the media identifier  213  are obscured from the database proprietor  116 , but the database proprietor  116  can still log impressions based on the modified values which can later be deciphered by the AME  114  after the AME  114  receives logged impressions from the database proprietor  116 . In some examples, the AME impressions collector  218  does not send site IDs, host site IDS, the media identifier  213  or modified versions thereof in the beacon response  222 . In such examples, the client device  102  provides the original, non-modified versions of the media identifier  213 , site IDs, host IDs, etc. to the database proprietor  116 . 
     In the illustrated example, the AME impression collector  218  maintains a modified ID mapping table  228  that maps original site IDs with modified (or substitute) site IDs, original host site IDs with modified host site IDs, and/or maps modified media identifiers to the media identifiers such as the media identifier  213  to obfuscate or hide such information from database proprietors such as the database proprietor  116 . Also in the illustrated example, the AME impressions collector  218  encrypts all of the information received in the beacon/impression request  212  and the modified information to prevent any intercepting parties from decoding the information. The AME impressions collector  218  of the illustrated example sends the encrypted information in the beacon response  222  to the client device  102  so that the client device  102  can send the encrypted information to the database proprietor  116  in the beacon/impression request  226 . In the illustrated example, the AME impressions collector  218  uses an encryption that can be decrypted by the database proprietor  116  site specified in the HTTP “302 Found” re-direct message. 
     Periodically or aperiodically, the impression data collected by the database proprietor  116  is provided to a DP impressions collector  230  of the AME  114  as, for example, batch data. As discussed above, some impressions logged by the client device  102  to the database proprietor  116  are misattributed by the database proprietor  116  to a wrong subscriber and, thus, to incorrect demographic information. During a data collecting and merging process to combine demographic and impression data from the AME  114  and the database proprietor  116 , demographics of impressions logged by the AME  114  for the client device  102  will not correspond to demographics of impressions logged by the database proprietor  116  because the database proprietor  116  has misattributed some impressions to the incorrect demographic information. Examples disclosed herein may be used to determine an impressions adjustment factor to correct/adjust impression-based data (e.g., total impressions and unique audience size) provided by the database proprietor  116 . 
     Additional examples that may be used to implement the beacon instruction processes of  FIG. 2  are disclosed in Mainak et al., U.S. Pat. No. 8,370,489, which is hereby incorporated herein by reference in its entirety. In addition, other examples that may be used to implement such beacon instructions are disclosed in Blumenau, U.S. Pat. No. 6,108,637, which is hereby incorporated herein by reference in its entirety. 
     In the example of  FIG. 2 , the AME  114  includes the example misattribution corrector  202  to correct unique audience values and impression counts that are based on impressions reported by client devices (e.g., the client device  102 ) for which the database proprietor  116  has misattributed some of the impressions to incorrect demographic information. The misattribution corrector  202  of the illustrated example is provided with an example audience adjustment factor determiner  232 , an example impressions adjustment factor determiner  234 , an example unique audience corrector  236 , and an example impressions corrector  238 . 
     The example audience adjustment factor determiner  232  of  FIG. 2  is provided to calculate a unique audience (UA) adjustment factor representative of an inaccurate UA size that is based on misattributed impressions relative to a UA size that is based on accurately attributed impressions. As discussed above, misattribution occurs when the database proprietor  116  identifies the wrong person as being a current user of the client device  102  when the client device reports an impression for accessed media to the database proprietor  116 . The example impressions adjustment factor determiner  234  is provided to calculate an impressions adjustment factor representative of an amount of misattributed impressions relative to an amount of correctly attributed impressions. 
     The example unique audience corrector  236  of  FIG. 2  is provided to correct unique audience sizes or quantities by applying the impressions adjustment factor (determined by the impressions adjustment factor determiner  234 ) to total unique audience sizes corresponding to total impressions collected by the AME  114 . The example impressions corrector  238  is provided to correct an impressions count by applying the impressions adjustment factor (determined by the impressions adjustment factor determiner  234 ) to the total number of impressions collected by the AME  114 . 
     Although the misattribution corrector  202  is shown in the illustrated example as being located in the AME  114 , the misattribution corrector  202  may alternatively be located at any other location such as at the database proprietor  116  or at any other suitable location (e.g., location(s) separate from the AME  114  and the database proprietor  116 ). In addition, although the AME impressions collector  218 , the modified ID map  228 , and the DP impressions collector  230  are shown separate from the misattribution corrector  202 , one or more of the AME impressions collector  218 , the modified ID map  228 , and/or the DP impressions collector  230  may be implemented in the misattribution corrector  202 . 
     While an example manner of implementing the example misattribution corrector  202 , the example impressions collector  218 , the example modified ID map  228 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and the example impressions corrector  238  is illustrated in  FIG. 2 , one or more of the elements, processes and/or devices illustrated in  FIG. 2  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example misattribution corrector  202 , the example AME impressions collector  218 , the example modified ID map  228 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and/or the example impressions corrector  238  of  FIG. 2  may be implemented by hardware, software, firmware and/or any combination of hardware, software, and/or firmware. Thus, for example, any of the example misattribution corrector  202 , the example AME impressions collector  218 , the example modified ID map  228 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and/or the example impressions corrector  238  could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)), and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example misattribution corrector  202 , the example AME impressions collector  218 , the example modified ID map  228 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and/or the example impressions corrector  238  is/are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example misattribution corrector  202 , the example impressions collector  218 , the example modified ID map  228 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and/or the example impressions corrector  238  of  FIG. 2  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 2 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
     Examples disclosed herein to correct impression-based data (e.g., total impressions and unique audience size) provided by the database proprietor  116  involve generating an adjustment factor based on impressions collected by the AME  116  and correctly attributed to demographic information for corresponding AME panelists. The misattribution corrector  202  of  FIG. 2  may be implemented using the example techniques below to correct impression-based data that is based on impressions of which some are misattributed to the wrong demographic information by the database proprietor  116 . 
     Examples disclosed herein involve using impressions logged by the AME  114  in association with demographic data collected from AME panel members to calculate an audience adjustment factor using example Equation 1 below and an impression adjustment factor using example Equation 2 below. Audience adjustment factors determined using example Equation 1 can be used to correct unique audience size values having inaccuracies due to misattributions of impressions by database proprietors. Impression adjustment factors determined using example Equation 2 below can be used to correct impression quantities having inaccuracies due to misattributions of impressions by database proprietors. 
     In the illustrated example of  FIG. 2 , the audience adjustment factor determiner  232  can use example Equation 1 below to determine an audience adjustment factor (f i,j ) for persons in a demographic group (j) that accessed media (i). 
     
       
         
           
             
               
                 
                   
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     In example Equation 1 above, f i,j  is the adjustment factor for a unique audience (UA) size of a particular demographic group (j) that accessed media (i), F i,j  is a database proprietor (DP) UA count of the number of AME panelists of the AME  114  that the database proprietor  116  observes (e.g., recognizes, identifies, logs impressions for, etc.) in the demographic group (j) as accessing the media (i), and T i,j  is an AME UA count of AME panelists that the AME  114  observes in the demographic group (j) as accessing the media (i). 
     In the illustrated example of  FIG. 2 , the impressions adjustment factor determiner  234  employs example Equation 2 below to determine an impressions adjustment factor (k i,j ) for persons in a demographic group (j) that accessed media (i). 
     
       
         
           
             
               
                 
                   
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     In example Equation 2 above, k i,j  is the impressions adjustment factor for impressions logged for a particular demographic group (j) that accessed media (i), R i,j  is a DP UA count of the number of AME panelists of the AME  114  that the database proprietor  116  observes (e.g., recognizes, identifies, logs impressions for, etc.) in the demographic group (j) as accessing the media (i), Q i,j  is an AME UA count of AME panelists that the AME  114  observes in the demographic group (j) as accessing the media (i), and S i  is the total AME impressions of AME panelists (summed across all demographic groups) that accessed media (i). 
       FIG. 3  illustrates an example table  300  with example AME impressions  302  collected by the AME  114  and example DP impressions  304  collected by the database proprietor  116  for different demographic groups (e.g., females younger than 50 years (F&lt;50), females 50 years old and older (F&gt;=50), males younger than 50 years (M&lt;50), and males 50 years old and older (M&gt;=50)). The example AME impressions  304  and the example DP impressions  304  shown in the example table  300  are development or test impressions that are collected by the AME  114  and the DP  116  during an adjustment factors development phase (e.g., an adjustment factors development phase  802  of  FIG. 8 ) with the purpose of calculating adjustment factors (e.g., audience adjustment (AA) factors  402  of  FIGS. 4 and 6  and impression adjustment (IA) factors  502  of  FIGS. 5 and 6 ) that can be subsequently used on large logs of real impressions collected by the database proprietor  116  to correct for impression misattributions that affect unique audience sizes and impression counts that are generated using the database proprietor&#39;s logged impressions. 
     In the illustrated example of  FIG. 3 , the DP impressions  304  have an example misattribution error  308  for impression #9 (IMP #9). That is, the impressions  302 ,  304  collected by both the AME  114  and the database proprietor  116  are based on client devices (e.g., the client device  102 ) having users that are both (1) AME panelists of the AME  114  and (2) registered subscribers of the database proprietor  116 . When the AME  114  logs an impression based on, for example, the beacon/impression request  212  of  FIG. 2  from a panelist of the AME  114 , the AME  114  logs an accurate impression. In the illustrated example of  FIG. 3 , such AME impressions  302  are also referred to as truth impressions  302  because the AME  114  regards them as correctly associated with corresponding demographic information of the current user of the client device  102 . In some examples, to assure the accuracy of the AME impressions  302 , the AME  114  incentivizes (e.g., through cash or other rewards) AME panel members to login to an AME website whenever the AME panel members begin using a client device  102 . In this manner, the AME  114  can accurately set and/or associate an AME ID (e.g., the device/user identifier  214  of  FIG. 2 ) with an AME panelist that is currently using the client device  102 . 
     Unlike the known accuracy, or truth, of the AME impressions  302 , there are no assurances that the DP impressions  304  are accurately associated with correct demographic information. That is, subscribers of the database proprietor  116  may not be incentivized to login to a website or service of the database proprietor  116  when the subscribers begin using a client device  102 . As such, the database proprietor  116  is sometimes unable to accurately set and/or associate a DP ID (e.g., the device/user identifier  227  of  FIG. 2 ) with a person that is currently using the client device  102 . The misattributions present in the development or test impressions of the table  300  of  FIG. 3  are representative of the types of misattributions that the database proprietor  116  is likely to make when logging impressions for persons that may or may not be AME panelists and/or may or may not be known to the database proprietor  116 . Therefore, calculating adjustment factors based on the development impressions of the table  300  of  FIG. 3  results in adjustment factors that can be used to correct for misattributions in impressions subsequently collected by the database proprietor  116  for other users. 
     In the illustrated example of  FIG. 3 , the example misattribution error  308  at impression #9 is created when the database proprietor  116  mis-recognizes an impression reported by the client device  102  (e.g., via the beacon/impression request  226  of  FIG. 2 ) as being associated with demographic information for a male (M) of age 30. In the example table  300  of  FIG. 3 , a correct demographic impression at IMP #9 logged by the AME  114  for the same person (e.g., via the beacon/impression request  212  of  FIG. 2 ) shows that the correct demographics indicate that the actual person corresponding to the impression is a female (F) of age 29. Example Equations 1 and 2 above may be used to correct unique audience sizes and total impression counts that are affected by misattribution errors such as the misattribution error  308  of  FIG. 3 . 
       FIG. 4  illustrates an example table  400  with example audience adjustment (AA) factors  402  (e.g., the audience adjustment factor (f i,j ) of Equation 1 above) for unique audience sizes of different demographic (DEMO) groups. Based on the AME impressions  302  of  FIG. 3 , the audience adjustment factor determiner  232  of  FIG. 2  can use Equation 1 above to calculate the example audience adjustment factors  402  for different demographic groups (j) that access particular media (i). The example table  400  shows AME UA sizes  404  and example DP UA sizes  406  for different demographic groups. The example AME UA sizes  404  correspond to the term (T i,j ) of Equation 1 above, and the DP UA sizes  406  correspond to the term (F i,j ) of Equation 1 above. In the illustrated example of  FIG. 4 , the AME UA sizes  404  show that the AME impressions  302  of  FIG. 3  include three (3) unique audience members of the F&lt;50 demo group, one (1) unique audience member of the F&gt;=50 demo group, two (2) unique audience members of the M&lt;50 demo group, and one (1) unique audience member of the M&gt;=50 demo group. The example DP UA sizes  406  show that the DP impressions  304  of  FIG. 3  include two (2) unique audience members of the F&lt;50 demo group, one (1) unique audience member of the F&gt;=50 demo group, two (2) unique audience members of the M&lt;50 demo group, and one (1) unique audience member of the M&gt;=50 demo group. 
     The example DP UA sizes  406  have a misattribution-based error  410  for the F&lt;50 demo group which results from the misattribution error  308  of  FIG. 3 . That is, the misattribution error  308  of  FIG. 3  mistakenly identifies impression  9  (IMP #9) as corresponding to a male (M) of age 30 rather than the correct demographic of female (F) of age 29, as noted in the AME impression  302 . Because of the misattribution error  308  of  FIG. 3 , impression  9  (IMP #9) for the DP impressions  304  is not counted for a female (F) of age 29. Therefore, the DP UA  406  of  FIG. 4  for the F&lt;50 demo group is only two (2), which is less than the correct (truth) unique audience for the F&lt;50 demo group of three (3) as shown by the corresponding AME UA size  404 . Because there were no other misattribution errors in the example impressions of  FIG. 3 , the DP UA sizes  406  match corresponding AME UA sizes  404  for the other demo groups. 
     In the illustrated example, the audience adjustment factor determiner  232  of  FIG. 2  uses Equation 1 above to determine the AA factors  402 . For example, for each of the demo groups F&lt;50, F&gt;=50, M&lt;50, and M&gt;=50, the audience adjustment factor determiner  232  divides the corresponding AME UA  404  (T i,j ) by the corresponding DP UA  406  (F i,j ) to determine the corresponding AA factor  402  for that demo group. As shown in the example table  400 , the AA factor  402  corresponding to the DP UA  406  having the misattribution-based error  410 , the corresponding AA factor  402  is 0.67 (e.g., T i,j /F i,j =&gt;3/2=0.67). 
       FIG. 5  illustrates an example table  500  with example impression adjustment (IA) factors  502  (e.g., the impressions adjustment factor (k i,j ) of Equation 2 above) for total AME impression counts  504  and total DP impression counts  506  of different demographic groups (j) determined based on the example AME impressions  302  and the example DP impressions  304  of  FIG. 3 . In the illustrated example of  FIG. 5 , a misattribution-based error  508  occurs in association with the F&lt;50 demographic group, and a misattribution-based error  510  occurs in association with the M&lt;50 demographic group. The misattribution-based errors  508 ,  510  occur because of the misattribution error  308  of  FIG. 3 . That is, since the misattribution error  308  incorrectly indicates a male (M) of age 30 instead of the correct female (F) of age 29, the DP impressions count  506  for the F&lt;50 demographic group has one fewer impression than the correct (truth) AME impressions count  504  for the F&lt;50 demographic group. In addition, the DP impressions count  506  for the M&lt;50 demographic group has one more impression than the correct (truth) AME impressions count for the M&lt;50 demographic group. 
     In the illustrated example, the impressions adjustment factor determiner  234  of  FIG. 2  uses Equation 2 above to determine the IA factors  502 . For example, for each of the demo groups F&lt;50, F&gt;=50, M&lt;50, and M&gt;=50, the impressions adjustment factor determiner  234  processes Equation 2 using the corresponding AME impressions  504  (Q i,j ) of  FIG. 5 , the corresponding DP impressions  506  (R i,j ) of  FIG. 5 , and the total AME impressions count (S i ) summed across all demographic groups, to determine the corresponding IA factor  502  for that demo group. For example, using Equation 2 above, the impressions adjustment factor determiner  234  subtracts the DP impressions  506  (R i,j ) of a particular demographic group from the AME impressions  504  (Q i,j ) of the same demographic group, and divides the resulting difference by the total AME impressions count (S i ) summed across all demographic groups (e.g., IA factor  502 =((AME impressions  504  (Q i,j ))−(DP impressions  506  (R i,j )))/(total AME impressions count (S i ))). 
     As shown in the example table  500 , the IA factor  502  corresponding to the F&lt;50 demographic group having the misattribution-based error  508  is 11.11%, and the IA factor  502  corresponding to the M&lt;50 demographic group having the misattribution-based error  510  is −11.11%. In the illustrated example, the IA factors  502  are 0.0% for the demographic groups not having misattribution-based errors. In the illustrated example, the impressions adjustment factor determiner  234  determines the misattribution-based error  508  of 11.11% for the F&lt;50 demographic group based on Equation 2 above by subtracting the DP impressions  506  (R i,j ) of 3 for the F&lt;50 demographic group shown in  FIG. 5  from the AME impressions  504  (Q i,j ) of 4 for the F&lt;50 demographic group shown in  FIG. 5 , and divides the resulting difference of one (1) by the total AME impressions count (S i ) of nine (9). Also in the illustrated example, the impressions adjustment factor determiner  234  determines the misattribution-based error  508  of −11.11% for the M&lt;50 demographic group based on Equation 2 above by subtracting the DP impressions  506  (R i,j ) of 4 for the M&lt;50 demographic group shown in  FIG. 5  from the AME impressions  504  (Q i,j ) of 3 for the M&lt;50 demographic group shown in  FIG. 5 , and divides the resulting difference of negative one (−1) by the total AME impressions count (S i ) of nine (9). 
     The IA factors  502  of the illustrated example are percentages of the total AME impressions count  504  summed across all demographic groups. Thus, the IA factor  502  of 11.11% corresponding to the F&lt;50 demographic group means that 11.11% of 9 total AME impressions (S i ) (i.e., the sum of all of the AME impressions  504  logged across all of the demographic groups shown in  FIG. 5 ) need to be added to the DP impressions count  506  for the F&lt;50 demographic group. For example, 11.11% of nine (9) total AME impressions is one (1), which can be added to the three (3) DP impressions count  506  for the F&lt;50 demographic group to make the DP impressions count  506  equal to the AME impressions count  504  for the F&lt;50 demographic group. In addition, the IA factor  502  of −11.11% corresponding to the M&lt;50 demographic group means that −11.11% of the nine (9) total AME impressions (i.e., the sum of all of the AME impressions  504  logged across all of the demographic groups shown in  FIG. 5 ) need to be added (or 11.11% need to be subtracted) from the DP impressions count  506  for the M&lt;50 demographic group. For example, −11.11% of nine (9) total AME impressions is negative one (−1), which can be added to the four (4) DP impressions count  506  for the M&lt;50 demographic group to make the DP impressions count  506  equal to the AME impressions count  504  for the M&lt;50 demographic group. Thus, the effect of the 11.11% IA factor  502  for the F&lt;50 demographic group and the −11.11% IA factor  502  for the M&lt;50 demographic group is that one (1) DP impression  506  is shifted away from the M&lt;50 demographic group to the F&lt;50 demographic group. In this manner, the total DP impressions  506  summed across all of the demographic groups remains the same after applying the IA factors  502 . 
       FIG. 6  illustrates an example table  600  with misattribution-corrected UA size values  602  and misattribution-corrected impression counts  604  based on the AA factors  402  of  FIG. 4  and the IA factors  502  of  FIG. 5  for different demographic groups. The data of example table  600  illustrates how UA size values and impression counts received by the AME  114  in the aggregate (e.g., not individual impression records) from the database proprietor  116  can be adjusted to correct for misattribution-based errors. The aggregate DP UA size values are shown in the example table  600  as DP decision tree (DT)-corrected UA size values  606 . The aggregate DP impression count values are shown in the example table  600  as DP DT-corrected impression counts  608 . To generate the DP DT-corrected UA size values  606  and the DP DT-corrected impression counts  608 , the database proprietor  116  performs a profile correction by applying a DT model on demographic data used to log impressions. That is, during initial registration with the database subscriber  116 , some subscribers may provide inaccurate demographic information and/or may omit certain demographic information. To fill in some of the missing demographic information in subscriber accounts, the database proprietor  116  processes the demographic data in subscriber accounts using a DT model that produces the most likely outcomes for the missing demographic data. Any suitable DT model can be used by the database proprietor  116  to correct profile data for subscribers of the database proprietor  116 . 
     In the illustrated example of  FIG. 6 , the example unique audience corrector  236  of  FIG. 2  applies the AA factors  402  to the DT-corrected UA size values  606  to determine the misattribution-corrected UA size values  602 . That is, the unique audience corrector  236  divides a DT-corrected UA size value  606  for a demographic group by a corresponding AA factor  402  for the same demographic group to calculate a corresponding misattribution-corrected UA size value  602  (e.g., (misattribution-corrected UA size)=(DT-corrected UA size)/(AA factor)). For example, for the F&lt;50 demographic group, the unique audience corrector  236  divides the DT-corrected UA size value  606  of 63,000 by the corresponding AA factor  402  of 0.67 to calculate the misattribution-corrected UA size value  602  of 94,500 (e.g., 94,500=63,000/0.67). Thus, using the AA factors  402  in this manner to calculate the misattribution-corrected UA size values  602  substantially reduces or eliminates the effects that misattributed impressions logged by the database proprietor  116  have on the DT-corrected UA size values  606 . 
     In the illustrated example of  FIG. 6 , the example impressions corrector  238  of  FIG. 2  applies the IA factors  502  to the DT-corrected impression counts  608  to determine the misattribution-corrected impression counts  604 . That is, the example impressions corrector  238  increases a DT-corrected impression count  608  for a demographic group based on a corresponding IA factor  502  for the same demographic group to calculate a corresponding misattribution-corrected impressions count  604 . In particular, the example impressions corrector  238  multiples an IA factor  502  for a demographic group by the total DP DT-corrected impressions count  612  summed across all of the demographic groups to determine a number of adjustment impressions by which to adjust the DP DT-corrected impressions count  608  for the same demographic group corresponding to the selected IA factor  502  (e.g., (adjustment impressions)=(IA factor)×(total cross-demographic DP DT-corrected impressions)). The example impressions corrector  238  then adds the calculated adjustment impressions to the corresponding DP DT-corrected impressions count  608  for the same demographic group to determine a corresponding misattribution-corrected impressions count  604  (e.g., (misattribution-corrected impressions count)=(DP DT-corrected impressions count  608 )+(adjustment impressions)). 
     For example, to determine the misattribution-corrected impressions  604  corresponding to the F&lt;50 demographic group, the example impressions corrector  238  of  FIG. 2  multiples the IA factor  502  of 11.11% for the F&lt;50 demographic group by the total DP DT-corrected impressions count  612  of 710,000 to calculate the adjustment impressions of 78,888. The example impressions corrector  238  then adds the 78,888 adjustment impressions to the corresponding DP DT-corrected impressions count  608  of 210,000 for the F&lt;50 demographic group to calculate the misattribution-corrected impressions count  604  of 288,889 for the F&lt;50 demographic group. 
     To determine the misattribution-corrected impressions  604  for the M&lt;50 demographic group, the example impressions corrector  238  of  FIG. 2  multiples the IA factor  502  of −11.11% for the M&lt;50 demographic group by the total DP DT-corrected impressions count  612  of 710,000 to calculate the adjustment impressions of −78,888. The example impressions corrector  238  then adds the −78,888 adjustment impressions to (or subtracts 78,888 from) the corresponding DP DT-corrected impressions count  608  of 165,000 for the M&lt;50 demographic group to calculate the misattribution-corrected impressions count  604  of 86,111 for the M&lt;50 demographic group. 
     An alternative technique to determine the misattribution-corrected unique audience sizes involves using impressions frequency values as described in connection with  FIG. 7 .  FIG. 7  illustrates an example table  700  with misattribution-corrected unique audience values  702  and misattribution-corrected impression counts  604  determined based on the IA factors  502  of  FIG. 5  and impression frequencies  706  for different demographic groups. As used herein, impressions frequency is a number of total impressions (e.g., a DP DT-corrected impression count  608  of  FIG. 6 ) divided by a quantity of unique audience members (e.g., a DT-corrected UA size value  606  of  FIG. 6 ) (e.g., frequency=impressions count/UA). For example, for the F&lt;50 demographic group, the database proprietor impressions frequency  706  is 3.33, which is calculated by dividing 210,000 DP DT-corrected impressions by 63,000 DP DT-corrected UA. In the illustrated example of  FIG. 7 , after the example impressions corrector  238  determines the misattributions-corrected impressions  604  based on the IA factors  502  as described above in connection with  FIG. 6 , the example unique audience corrector  236  divides the misattribution-corrected impressions  604  of 288,889 for the F&lt;50 demographic group by the DP frequency of 3.33 (for the F&lt;50 demographic group) to calculate a misattribution-corrected UA size  702  of 86,667. The frequency-based approach to determining misattribution-corrected impressions  704  preserves the impressions frequencies for the demographic groups. 
     As shown in  FIGS. 6 and 7 , the misattribution-corrected UA sizes  602  of  FIG. 6  are different from the misattribution-corrected UA sizes  702  of  FIG. 7 . In determining whether to use the AA factor approach described above in connection with  FIG. 6  or the impressions frequency approach described in connection with  FIG. 7  to determine misattribution-corrected UA sizes, both approaches can be applied over multiple iterations on test data for which true UA sizes are known. The approach that produces the most accurate misattribution-corrected UA sizes relative to the true UA sizes can then be selected for use on real impression data. Alternatively, the impression frequency approach may be selected if a party wishes to preserve impression frequency even if the accuracies of resulting misattribution-corrected UA sizes are not optimal. 
     An example advantage of example misattribution adjustment techniques disclosed herein is that the total DP DT-corrected impressions count  612  (e.g., 710,000 impressions in  FIGS. 6 and 7 ) remains the same after correcting the data for misattribution errors. That is, impressions are not changed, but are instead redistributed. For example, as shown in  FIGS. 6 and 7 , a total misattribution-corrected impressions count  614  across all demographic groups is 710,000, which is equal to the DP DT-corrected impressions count  612  of 710,000. 
       FIG. 8  is a flow diagram representative of machine readable instructions that may be executed to implement the misattribution corrector  202  of  FIG. 2  to determine the AA factors  402  of  FIGS. 4 and 6 , the IA factors  502  of  FIGS. 5, 6, and 7 , the misattribution-corrected unique audience sizes  602  of  FIG. 6 , the misattribution-corrected unique audience sizes  702  of  FIG. 7 , and the misattribution-corrected impression counts  604  of  FIGS. 6 and 7 . In this example, the machine readable instructions comprise one or more programs for execution by a processor such as the processor  912  shown in the example processor platform  900  discussed below in connection with  FIG. 9 . The program(s) may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor  912 , but the entire program and/or parts thereof could alternatively be executed by a device other than the processor  912  and/or embodied in firmware or dedicated hardware. Further, although the example program(s) is/are described with reference to the flowchart illustrated in  FIG. 8 , many other methods of implementing the example misattribution corrector  202  may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. 
     As mentioned above, the example process(es) of  FIG. 8  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, “tangible computer readable storage medium” and “tangible machine readable storage medium” are used interchangeably. Additionally or alternatively, the example process(es) of  FIG. 8  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, when the phrase “at least” is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term “comprising” is open ended. 
     The example flow diagram of  FIG. 8  is shown as two phases including an example adjustment factors development phase  802  and an example misattribution correction phase  804 . During the adjustment factors development phase  802 , the misattribution corrector  202  ( FIG. 2 ) determines the AA factors  402  ( FIGS. 4 and 6 ) and the IA factors  502  ( FIGS. 5 and 6 ) for different demographic groups based on development or test impressions such as the impressions shown in table  300  of  FIG. 3 . During the misattribution correction phase  804 , the misattribution corrector  202  corrects aggregate impression data (e.g., unique audience measures and total impression counts) generated based on impressions collected by the database proprietor  116  (and/or one or more other database proprietors). For example, the misattribution corrector  202  uses the AA factors  402  and/or the IA factors  502  to determine the misattribution corrected UA size values  602  of  FIG. 6 , the misattribution-corrected UA size values  702  of  FIG. 7 , and/or the misattribution-corrected impression counts  604  of  FIGS. 6 and 7  for different demographic groups. In some examples, the misattribution correction phase  804  may begin immediately after the adjustment factors development phase  802 . In other examples, the misattribution correction phase  804  may begin after a significant amount of time (e.g., hours, days, weeks, etc.) has passed following the completion of the adjustment factors development phase  802 . In some examples, the adjustment factors development phase  802  and the misattribution correction phase  804  may be implemented as part of a same program. In other examples, the adjustment factors development phase  802  and the misattribution correction phase  804  may be implemented as two separate programs. 
     The example adjustment factors development phase  802  of  FIG. 8  begins at block  806  at which the AME impressions collector  218  collects impressions from the client device  102 . For example, the AME impressions collector  218  collects impressions using the techniques described above in connection with  FIG. 2 . The DP impressions collector  230  obtains development impression records from the database proprietor  116  that correspond to AME panelists that are also subscribers of the database proprietor  116  (block  808 ). The misattribution corrector  202  selects a demographic group (block  810 ). For example, the misattribution corrector  202  selects one of the demographic groups of  FIGS. 4-7 . The example impressions adjustment factor determiner  234  ( FIG. 2 ) determines an IA factor  502  for the selected demographic group (block  812 ). For example, the impressions adjustment factor determiner  234  determines the IA factor  502  using Equation 2 above and/or the technique described above in connection with  FIG. 5 . 
     The example unique audience adjustment factor determiner  232  ( FIG. 2 ) determines an AA factor  402  for the selected demographic group (block  814 ). For example, the unique audience adjustment factor determiner  232  determines the AA factor  402  using Equation 1 above and/or the technique described above in connection with  FIG. 4 . The misattribution corrector  202  determines whether there is another demographic group for which to determine adjustment factors (block  816 ). If there is another demographic group, control returns to block  810 . If there is not another demographic group, the adjustment factors development phase  802  ends. In the illustrated example, after the adjustment factors development phase  802  ends, the misattribution correction phase  804  begins based on the IA factors  502  and the AA factors  402  determined during the adjustment factors development phase  802 . In some examples, the adjustment factors development phase  802  is repeated from time to time (e.g., after a number of days, weeks, months, etc.) to update the IA factors  502  and/or the AA factors  402 . For example, the ability of the database proprietor  116  to identify subscribers may change (e.g., increased or decreased accuracy) from time to time. As such, to increase the likelihood that the IA factors  502  and the AA factors  402  reflect such changes, the adjustment factors development phase  802  can be repeated from time to time. 
     In the misattribution correction phase  804 , the DP impressions collector  230  obtains the DP DT-corrected unique audience sizes  606  ( FIG. 6 ) and DP DT-corrected impression counts  608  ( FIG. 6 ) from the database proprietor  116  (block  818 ). The misattribution corrector  202  selects a demographic group (block  820 ). For example, the misattribution corrector  202  selects one of the demographic groups of  FIGS. 4-7 . The example impressions corrector  238  ( FIG. 2 ) determines a misattribution-corrected impressions count  604  ( FIGS. 6 and 7 ) based on the IA factor  502  for the selected demographic group (block  822 ). For example, the impressions corrector  238  can determine the misattribution-corrected impressions count  604  as described above in connection with  FIG. 6 . 
     The misattribution corrector  202  determines whether to use impressions frequency to determine a misattribution-corrected unique audience size (block  824 ). For example, the misattribution corrector  202  may check a configuration setting in a file, a program, and/or a hardware setting indicating whether to determine a misattribution-corrected unique audience size based on an impressions frequency  706  ( FIG. 7 ). If the misattribution corrector  202  determines that it should determine a misattribution-corrected unique audience size based on an impressions frequency  706 , the misattribution corrector  202  determines an impressions frequency  706  for the selected demographic profile (block  826 ). For example, the misattribution corrector  202  may determine the impressions frequency  706  for the selected demographic profile as described above in connection with  FIG. 7 . If the misattribution corrector  202  determines that it should not use an impressions frequency  706  to determine a misattribution-corrected unique audience size, control advances to block  828  without determining an impressions frequency  706 . In some examples, the impressions frequency  706  is determined by the database proprietor  116  and provided by the database proprietor  116  to the misattribution corrector  202  via the DP impressions collector  230 . In such examples, the misattribution corrector  202  does not need to determine the impressions frequency  706 . 
     At block  828 , the example unique audience corrector  236  ( FIG. 2 ) determines the misattribution-corrected UA size for the selected demographic group (block  828 ). For example, if the misattribution corrector  202  determined at block  824  that the impressions frequency  706  is to be used to determine the misattribution-corrected UA size  702  ( FIG. 7 ) for the selected demographic group, the unique audience corrector  236  determines the misattribution-corrected UA size  702  based on the impressions frequency  706  of block  826  as described above in connection with  FIG. 7 . Alternatively at block  828 , if the misattribution corrector  202  determined at block  824  that the impressions frequency  706  is not to be used to determine the misattribution-corrected UA size  602  ( FIG. 6 ) for the selected demographic group, the unique audience corrector  236  determines the misattribution-corrected UA size  602  based on the AA factor  402  ( FIG. 4 ) of the selected demographic group as described above in connection with  FIG. 6 . 
     The misattribution corrector  202  then determines whether there is another demographic group for which misattribution-adjusted impression counts or misattribution-adjusted UA sizes are to be determined (block  830 ). If there is another demographic group, control returns to block  820 . Otherwise, the example program of  FIG. 8  ends. 
       FIG. 9  is a block diagram of an example processor platform  900  capable of executing the instructions of  FIG. 9  to implement the misattribution corrector  202  of  FIG. 2 . The processor platform  900  can be, for example, a server, a personal computer, or any other type of computing device. 
     The processor platform  900  of the illustrated example includes a processor  912 . The processor  912  of the illustrated example is hardware. For example, the processor  912  can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer. 
     In the illustrated example, the processor  912  implements the example misattribution corrector  202 , the example AME impressions collector  218 , the example DP impressions collector  230 , the example audience adjustment factor determiner  232 , the example impressions adjustment factor determiner  234 , the example unique audience corrector  236 , and/or the example impressions corrector  238  described above in connection with  FIG. 2 . 
     The processor  912  of the illustrated example includes a local memory  913  (e.g., a cache). The processor  912  of the illustrated example is in communication with a main memory including a volatile memory  914  and a non-volatile memory  916  via a bus  918 . The volatile memory  914  may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory  816  may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory  914 ,  916  is controlled by a memory controller. 
     In the illustrated example, the local memory  913  stores the example modified ID map  228  described above in connection with  FIG. 2 . In other examples any one or more of the local memory  913 , the random access memory  914 , the read only memory  916 , and/or a mass storage device  928  may store the example modified ID map  228 . 
     The processor platform  900  of the illustrated example also includes an interface circuit  920 . The interface circuit  920  may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface. 
     In the illustrated example, one or more input devices  922  are connected to the interface circuit  920 . The input device(s)  922  permit(s) a user to enter data and commands into the processor  912 . The input device(s) can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system. 
     One or more output devices  924  are also connected to the interface circuit  920  of the illustrated example. The output devices  924  can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a light emitting diode (LED), a printer and/or speakers). The interface circuit  920  of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor. 
     The interface circuit  920  of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network  926  (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.). 
     The processor platform  900  of the illustrated example also includes one or more mass storage devices  928  for storing software and/or data. Examples of such mass storage devices  928  include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives, RAID systems, and digital versatile disk (DVD) drives. 
     Coded instructions  932  include the machine readable instructions of  FIG. 8  and may be stored in the mass storage device  928 , in the volatile memory  914 , in the non-volatile memory  916 , and/or on a removable tangible computer readable storage medium such as a CD or DVD. 
     From the foregoing, it will be appreciate that methods, apparatus and articles of manufacture have been disclosed which enhance the operations of a computer to improve the accuracy of impression-based data such as unique audience and impression counts so that computers and processing systems therein can be relied upon to produce audience analysis information with higher accuracies. In some examples, computer operations can be made more efficient based on the above equations and techniques for determining IA factors, AA factors, misattribution-corrected unique audience sizes, and misattribution-corrected impression counts. That is, through the use of these processes, computers can operate more efficiently by relatively quickly determining parameters and applying those parameters through the above disclosed techniques to determine the misattribution-corrected data. For example, using example processes disclosed herein, a computer can more efficiently and effectively identify misattribution errors (e.g., the misattribution error  308  of FIG.  3 ) in development or test data logged by the AME  114  and the database proprietor  116  without using large amounts of network communication bandwidth (e.g., conserving network communication bandwidth) and without using large amounts of computer processing resources (e.g., conserving processing resources) to communicate with individual online users to request survey responses about their online media access habits and without needing to rely on such survey responses from such online users. Survey responses from online users can be inaccurate due to inabilities or unwillingness of users to recollect online media accesses. Survey responses can also be incomplete, which could require additional processor resources to identify and supplement incomplete survey responses. As such, examples disclosed herein more efficiently and effectively determine misattribution-corrected data. Such misattribution-corrected data is useful in subsequent processing for identifying exposure performances of different media so that media providers, advertisers, product manufacturers, and/or service providers can make more informed decisions on how to spend advertising dollars and/or media production and distribution dollars. 
     Furthermore, example methods, apparatus, and/or articles of manufacture disclosed herein identify and overcome inaccuracies in impressions and/or aggregate impression-based data provided by database proprietors. For example, example methods, apparatus, and/or articles of manufacture disclosed herein overcome the technical problem of counting impressions and determining unique audiences of media on media devices that are shared by multiple people. Example methods, apparatus, and/or articles of manufacture disclosed herein solve this problem without forcing such media devices to be used by only a single person and without forcing people to always login to their subscriber accounts of database proprietors. By not forcing logins into database proprietor accounts, examples disclosed herein do not force additional network communications to be employed, thus, reducing network traffic. 
     Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.