Proportionate sampling is a variation of stratified random sampling. We use this technique when our subgroups vary dramatically in size in our population. For example, we are interested in risk taking among college students and suspect that risk taking might differ between smokers and nonsmokers. Given increasing societal pressures against smoking, there are many fewer smokers on campus than nonsmokers. Rather than take equal numbers of smokers and nonsmokers, we want each group represented in their proportions in the population.

Proportionate sampling strategies begin by stratifying the population into relevant subgroups and then random sampling within each subgroup. The number of participants that we recruit from each subgroup is equal to their proportion in the population.