DEFINITION of 'Sample'
A subset containing the characteristics of a larger population. Samples are used in statistical testing when population sizes are too large for the test to include all possible members or observations. A sample should represent the whole population and not reflect bias toward a specific attribute.
INVESTOPEDIA EXPLAINS 'Sample'
A sample is a smaller, manageable version of a larger group. For example, if you wanted to test an investment strategy on past stock data, you would have an enormous number of stocks to test. Instead of testing the strategy on every stock, you would use a sample, which allows you to draw statistical insights from a smaller group of stocks. The sample should not contain any bias, such as the survivorship bias, where you might only use stocks that have survived the entire length of time you wish to test. Choosing a sample randomly should eliminate the possibilities of bias.

Sampling Distribution
A probability distribution of a statistic obtained through a ... 
Normal Distribution
A probability distribution that plots all of its values in a ... 
LookAhead Bias
Bias created by the use of information or data in a study or ... 
Sampling Error
A statistical error to which an analyst exposes a model simply ... 
Survivorship Bias
The tendency for mutual funds with poor performance to be dropped ... 
Attribute Bias
The tendency of stocks selected by a quantitative technique or ...

What are some examples of stratified random sampling?
Simple random sampling is a sample of individuals that exist in a population; the individuals are randomly selected from ... Read Full Answer >>

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