Definition

A small fraction or portion of the population of interest, selected for the purpose of estimating a population characteristic (parameter), or drawing an inference about the population. When making decisions, it is usually unnecessary (and sometimes impossible) to study the entire population about which the decision is made - instead, a carefully selected sample can do the same task for a fraction of time and cost.

Most statistical tools used for data analysis are based on the assumption that the sample is drawn at random, where all individual members/units of the population have an equal chance of being selected. This method of selection gives a reasonable assurance that the sample is representative of the population from which it was selected, as well as the independence of individual sample observations.

See Also

Random Sample
Sampling