In statistics, a population consists of all members of a group of interest. Populations can vary in size and include people, animals, plants, or objects. Since it may be impractical to study every member of a population, a sample is sometimes selected to represent the population and obtain data.

For example, suppose there is a study that examines high school students' attitudes in Boston towards mathematics. In this case, the population consists of all high school students in Boston. Since it is impractical to study every student, a sample can be taken by using sampling methods.