Sampling

The act or process of selecting a sample – usually with the goal of selecting an appropriate or suitable sample – especially the selection of events, objects, people, etc., at random from a population for the purpose of determining its characteristics and analyzing the sample to yield useful estimates and information with which to test hypotheses about the population;

inferring the behaviour of a whole category by studying a fraction or segment of it.

(see also: biased sampling, statistic, Law of large numbers, Margin of error, sample bias, selection bias)