A sample is a subset of a population that is obtained through some process, possibly random selection or selection based on a certain set of criteria, for the purposes of investigating the properties of the underlying parent population. In particular, statistical quantities determined directly from the sample (such as sample central moments, sample raw moments, sample mean, sample variance, etc.) can be used as estimators for the corresponding properties of the underlying distribution.

The process of obtaining a sample is known as sampling, and the number of members in a sample is called the sample size.

REFERENCES:

Gonick, L. and Smith, W. The Cartoon Guide to Statistics. New York: Harper Perennial, p. 91, 1993.

Kenney, J. F. and Keeping, E. S. "Populations and Samples." §7.1 in Mathematics of Statistics, Pt. 1, 3rd ed. Princeton, NJ: Van Nostrand, pp. 90-91, 1962.