Is it ensure, insure, or assure?
c.1300, "something which confirms a proposition or statement," from Anglo-French saumple, a shortening of Old French essample, from Latin exemplum "a sample" (see example). Meaning "small quantity (of something) from which the general quality (of the whole) may be inferred" (usually in a commercial sense) is recorded from early 15c.; sense of "specimen for scientific sampling" is from 1878. As an adjective from 1820.
"to test by taking a sample," 1767, from sample (n.). Earlier "to be a match for" (1590s). Related: Sampled; sampling.
In statistics, a group drawn from a larger population and used to estimate the characteristics of the whole population.
Note: Opinion polls use small groups of people, often selected at random, as a sample of the opinions of the general public.