representative sample

n. A sample that is selected to have characteristics similar to those of the larger target population on variables of interest to the study or investigation. A representative sample is selected by dividing the population into nonoverlapping and collectively exhaustive subpopulations or strata (the number of strata depends on the target of the study and the relevant grouping characteristics). Sample members are then selected from each stratum or subgroup in proportion to the population. The members of each stratum are pooled to form the overall representative sample. – BJM