As another example, like the income example presented for the mean, consider a room with 10 people who have incomes of $10, $20, $20, $40, $50, $60, $90, $90, $100, and $1,000,000. Here, the median is $55, because $55 is the average of the two middle numbers, $50 and $60. If the extreme value of $1,000,000 is ignored, the mean is $53. In this case, the median is close to the value obtained when the extreme value is thrown out. The median solves the problem of extreme values as described in the definition of mean above.
The mode is the most frequent item of data. For example, the most common letter in English is the letter "e". We would say that "e" is the mode of the distribution of the letters.
As another example, if there are 10 people in a room with incomes of $10, $20, $20, $40, $50, $60, $90, $90, $90, $100, and $1,000,000, then the mode is $90, because $90 occurs three times and all other values occur fewer than three times.
There can be more than one mode. For example, if there are 10 people in a room with incomes of $10, $20, $20, $20, $50, $60, $90, $90, $90, $100, and $1,000,000, the modes are $20 and $90. This is bi-modal, or has two modes. Bi-modality is very common, and it often indicates that the data is the combination of two different groups. For instance, the average height of all adults in the U.S. has a bi-modal distribution. This is because males and females have separate average heights of 1.763 m (5 ft 9 + 1⁄2 in) for men and 1.622 m (5 ft 4 in) for women. These peaks are apparent when both groups are combined.
The mode is the only form of average that can be used for data that can not be put in order.
Another thing we can say about a set of data is how spread out it is. A common way to describe the spread of a set of data is the standard deviation. If the standard deviation of a set of data is small, then most of the data is very close to the average. If the standard deviation is large, though, then a lot of the data is very different from the average.
The standard deviation of a sample is generally different from the standard deviation of its originating population . Because of that, we write formula_7 for population standard deviation, and formula_8 for sample standard deviation.
If the data follows the common pattern called the normal distribution, then it is very useful to know the standard deviation. If the data follows this pattern (we would say the data is "normally distributed"), about 68 of every 100 pieces of data will be off the average by less than the standard deviation. Not only that, but about 95 of every 100 measurements will be off the average by less than two times the standard deviation, and about 997 in 1000 will be closer to the average by less than three standard deviations.
We also can use statistics to find out that some percent, percentile, number, or fraction of people or things in a group do something or fit in a certain category.
For example, social scientists used statistics to find out that 49% of people in the world are males.
In order to support statisticians, many statistical software have been developed:
Speed
Speed is the distance of a moving object in a given amount of time. Speed is a measure of how fast something is moving. The average speed of an object in a certain time is the distance the object travelled divided by the time. Speed is also the distance covered by an object per unit time.
To find speed formula_1,
formula_2formula_3
where formula_4 is the distance and formula_5 is the time that has gone by.
There are many units of measurement for speed. For example, an object's speed can be measured in
When an object changes speed, it gets faster or slower. If the speed of the object increases, it is called acceleration. If the object gets slower, and the speed decreases, it is called deceleration, or negative acceleration.
Server log
A server log records what is happening on a server at any time. For example, an HTTP server runs a web site.
Server
In net jargon, a server is a computer that serves many kinds of information to a user or client machine. Usually a server will only do a few things for many clients. Every type of thing a server does is called a service. Services are used by other computers that are called clients. The relationship between client and server is called a client-server relationship. For example, Wikipedia has web servers which have a service for sending web pages over the Internet. Your client computer talks to Wikipedia's web page service to get web pages for you. A server can also host internet games, share files, and give access to peripheral equipment such as printers. In simple words, the individual computers are connected to some powerful computers called servers. These store files and information in the form of website. With an Internet connection, different users anywhere in the world can access these files.
For servers and clients to talk to each other, they need to be connected to a network. They need to use the same communication protocol, a set way for machines to talk to other machines. It is like a language. For example, the Wikipedia server runs the HTTP to send web sites to your computer, and your computer uses the HTTP Protocol to ask Wikipedia for pages.
Usually, servers are specially made to be more powerful and reliable. They are usually more expensive than normal computers. Sometimes, servers can be clustered, which means many servers are working together to do one service.
The server might slow down if there are too many people accessing the server at the same time, resulting in a high load. An overloaded server might also shut itself down automatically.
In a peer-to-peer system, every computer is both a client and a server to the others. This is commonly put into file sharing and VOIP. However, this can help in attempts at piracy.
Typical server operating systems are Linux, FreeBSD, NetBSD, and OpenBSD. Unlike other computers, a server often has no monitor, keyboard, or mouse. When a server doesn't have to do very much, server software can run on a computer that is also doing other things.
A web server is a type of server that is used to host websites.
Examples of web server software include Apache or IIS. A web server can host one, or many, websites. The default port for a web server to listen to is port 80 (HTTP) or 443 (HTTPS).
Some web servers do other things than just serving a web page. For example, they may have something called SSI that makes building a website easier.
Web servers use services like CGI to let software on the server make web pages. Some of the programming languages that can use CGI are scripting languages like Perl, Python, PHP, or ASP. Some are compiled languages like C++ or Java.
Simile
A simile is a figure of speech that compares two different things, usually by using the words 'like' or 'as'. It is used to make a "direct and clear comparison between two things .Similes" may be confused with metaphors, which do the same kind of thing. Similes use comparisons, with the words 'like' or 'as'. Metaphors use indirect comparisons, without the words 'like' or 'as'.
State
In politics, a state is a country which has control over a geographic area or territory. States have three main features:
There are different forms of government a state may have, for example a republic or a monarchy. Sometimes states form their own countries. At other times many states work together to form a country (like the United States). Most states also have armed forces, civil service, law and police.
The definition above is very broad. It is based on ideas by Georg Jellinek (1851-1911). Other people had other ideas:
Because of the different definitions, there's no universally accepted definition of state. The one given at the start of the article is now part of international law.
The earliest states were just human settlements. A group of farmers and merchants working together could be 'states' since people can control them and protect them.