| **National Center    for     Health Statistics            Division of Data     Services            6525 Belcrest Road     Hyattsville, MD     20782-2003     (301)458-4636      **

 

**National Health Interview Survey    (NHIS)NCHS Home | NHIS Home | Description | 1997 NHIS | 1998 NHIS1999 NHIS | NHIS    on Disability | News Releases and    Fact SheetsData Highlights | Coming Events | Methods    | PublicationsMicro-data | Related    Links | Other Federal AgenciesSearch NCHS | Contact us**
**Variance Estimation for Person    Data Using SUDAAN and the National Health Interview Survey (NHIS) Public-Use Person Data    Files, 1987-94**

**CD-ROM Version****Design Information    Available on the NHIS Public Use Basic Health and Demographic and Current Health Topic    Data Files.**    Not all of the following variables are used for all methods of variance approximation.    Field locations may change on some files; the user should check the data format for each    file.
***Variable         name******Tape location******Field label******Values***STRATUM179-181'FULL SAMPLE STRATUM IDENTIFIER'CSTRATUM187-188'PSEUDO PSU CODES', first two columns1, 2, ..., 62CPSU189'PSEUDO PSU CODES', last column1, 2, 3, 4SUB178'TYPE OF SUBSTRATUM'0, 1, 2SSU5-12concatenation of 'PROCESSING QUARTER',        'RANDOM RECODE OF PSU NUMBER',        'WEEK-CENSUS CODE' and 'SEGMENT        NUMBER'TYPE_PSU185'TYPE OF PSU',        Self-representing PSU         Nonself-representing PSU        1, 4        3, 6WTF207-212'FINAL BASIC WEIGHT
 

**Method 1 - Single Stage PSU's    Sampled With Replacement within Strata Design for 1987-1994 NHIS.**    This method is statistically less efficient than the method described below but is more    flexible. This method requires no recoding of design variables, may be applicable to many    complex survey sample design computer programs, and covers the 1987-1994 NHIS survey    years. Using the variables CSTRATUM, CPSU, and WTF, the PSU unit CPSU is treated as being    sampled with replacement within stratum unit CSTRATUM. The data file needs to be sorted    only by CSTRATUM and CPSU prior to invoking SUDAAN.     For the above simplification of the NHIS sample design structure, use the following SUDAAN    design statements:**PROC** (procedure name) **DESIGN = WR;****NEST CSTRATUM CPSU;**

**Method 2 - Multistage stratified sampling design for the 1987-1994 NHIS.**    This design provides for more statistically efficient variance estimation than Method 1.    Method 2 makes fewer simplifications of the NHIS sample design structure but is only    applicable to SUDAAN. This method also requires recodes of the design variables and is    only applicable to survey years 1987-94 NHIS person data.    Prior to use of this method the following recoding must be done on the NHIS file. This    example is in SAS but other programming languages may be used.    If (TYPE_PSU = 1 or TYPE_PSU = 4) then do;PSU    = 1;POPPSU    = 0;END;    If (TYPE_PSU = 3 or TYPE_PSU = 6) then do;PSU    = CPSU;POPPSU    = -1;END;    This recode creates two new variables on each record, PSU and POPPSU, for use by SUDAAN's    NEST and TOTCNT statements. For more information on the purpose of these statements refer    to SUDAAN documentation. With these additional variables, use the following SUDAAN code    for NHIS data-sets assuming a multistage stratified sampling design.    Before running SUDAAN against the data file, however, sort the input file by the NEST    variables (STRATUM, PSU, SUB, and SSU).    For SUDAAN, describe the NHIS sampling design as follows:**PROC**    (procedure name) **DESIGN = WOR;****NEST    STRATUM PSU SUB SSU /MISSUNIT;****TOTCNT POPPSU _ZERO_ _MINUS1_ _ZERO_;**    Caution. This method assumes that ALL records on the BASIC HEALTH AND DEMOGRAPHIC (BHD) or    CURRENT HEALTH TOPIC (CHT) file are being used. If, however, you keep only selected    records on a file, e.g., persons aged 65+ (which may delete all records from one or more    SSUs), care must be taken to preserve the integrity of the sampling design.     All Self-Representing (SR) SSU's (TYPE_PSU = 1 or 4) listed on the FULL NHIS file (BHD or    CHT) must have at least one representative on the data file used for input to SUDAAN.    Moreover, all Nonself-representing (NSR) PSU's must  have at least one record for a    person on this data file. The NEST variables (STRATUM, PSU, SUB, and SSU) along with the    weight variable must be on each  record of the analysis file.

 

**NCHS Home    | NHIS Home | Description    | 1997 NHIS | 1998    NHIS1999 NHIS | NHIS    on Disability | News Releases and    Fact SheetsData Highlights | Coming Events | Methods    | PublicationsMicro-data | Related    Links | Other Federal AgenciesSearch NCHS | Contact us**
**CDC Home | Search    | Health Topics A-Z**
This page last reviewed July 26, 2000

**U.S.    DEPARTMENT OF HEALTH AND HUMAN SERVICES****Centers    for Disease Control and Prevention**    National Center for Health Statistics    Division of Data Services     Hyattsville, MD    20782-2003    (301) 458-4636
 

 

  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|