Sample

In statistics, a data sample is a set of data collected from a statistical population by a defined procedure. Population denotes a set of similar items or events which is of interest for some question or experiment.

Sample size
The determination of the sample size (the act of choosing the number of observations or replicates to include in a statistical sample) is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. In practice, the sample size used in a study is determined based on the expense of data collection, and the need to have sufficient statistical power. Larger sample sizes generally lead to increased precision when estimating unknown parameters.

WikiProject Statistics
For practical reasons, sample sizes within the WikiProject Statistics are divided into three categories: