Samples are used in much of the research conducted in both the social and natural/physical sciences. Even in the fields of history, music, and English, samples are often used in empirical investigations. Because the quality of the sample(s) used in a study has such an important bearing on the trustworthiness of a researcher's conclusions, here the following six critical aspects are considered:

• The definition of sample
• Why researchers use samples
• How sample data are used
• What kinds of samples researchers use
• Why the concept of “sampling error” is important
• The misconceptions people have about samples