A sample is a subset of a population.
Since it is
usually impractical to test every member of a population, a sample from the
population is typically the best approach available.
generally require that sampling be random
some types of sampling (such as those used in voter polling) seek to make the
sample as representative of the population as possible by choosing the sample
to resemble the population on the most important characteristics.
See also: biased
and random sample