What is a 'Sample'
A sample is 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.
BREAKING DOWN '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
A process used in statistical analysis in which a predetermined ... 
Sampling Error
A statistical error to which an analyst exposes a model simply ... 
Sampling Distribution
A probability distribution of a statistic obtained through a ... 
Systematic Sampling
A type of probability sampling method in which sample members ... 
Simple Random Sample
A subset of a statistical population in which each member of ... 
Sample Selection Bias
A type of bias caused by choosing nonrandom data for statistical ...

Fundamental Analysis
How Does Sampling Work?
Sampling is a term used in statistics that describes methods of selecting a predefined representative number of data from a larger data population. 
Professionals
Sampling and Estimation
CFA Level 1  Sampling and Estimation sampling error, in depth information on confidence intervals and tdistributions 
Economics
What is Systematic Sampling?
Systematic sampling is similar to random sampling, but it uses a pattern for the selection of the sample. 
Fundamental Analysis
What is a Representative Sample?
In statistics, a representative sample accurately represents the makeup of various subgroups in an entire data pool. 
Fundamental Analysis
Explaining Standard Error
Standard error is a statistical term that measures the accuracy with which a sample represents a population. 
Fundamental Analysis
Understanding the Simple Random Sample
A simple random sample is a subset of a statistical population in which each member of the subset has an equal probability of being chosen. 
Fundamental Analysis
Explaining the Central Limit Theorem
Central limit theorem is a fundamental concept in probability theory. 
Investing
How to Use Stratified Random Sampling
Stratified random sampling is a technique best used with a sample population easily broken into distinct subgroups. Samples are then taken from each subgroup based on the ratio of the subgroupâ€™s ... 
Professionals
Sampling Considerations
CFA Level 1  Sampling Considerations 
Professionals
Interpreting Statistical Results
CFA Level 1  Test Statistics and Interpreting Results

How can a representative sample lead to sampling bias?
Learn how using representative samples alone is not enough to make sampling bias negligible and why elements such as randomization ... Read Answer >> 
What percentage of the population do you need in a representative sample?
Learn about representative samples and how they are used in conjunction with other strategies to create useful data with ... Read Answer >> 
What's the difference between a representative sample and a convenience sample?
Learn the difference between convenience sampling and representative sampling and the advantages and disadvantages of each ... Read Answer >> 
What's the difference between a representative sample and a random sample?
Explore the differences between representative samples and random samples, and discover how they are often used in tandem ... Read Answer >> 
What is the difference between systematic sampling and cluster sampling?
Learn about the differences between systematic sampling and cluster sampling, including how the samples are created for each ... Read Answer >> 
What's the difference between a representative sample and an unbiased sample?
Discover how the different techniques used to select representative samples and unbiased samples are often exploited and ... Read Answer >>