Researchers need to select individuals who are part of the population for their studies. That is, from all possible people or organizations in the population, they select a sample for study from the population. A sample is a subgroup of the population that the researcher plans to study for generalizing about the population. As illustrated in Figure 7.1 , researchers can select different possible samples from populations of interest. For example, a researcher may be interested in elementary principles (the population) and selects a collection of principles from around the state as the sample for a research study.