APA Dictionary of Psychology

a form of stratified sampling in which one draws cases for study from certain groups (e.g., gender, race/ethnicity) in the proportions that are observed in the larger population. For example, if a university has 60% female students and 40% male students, a researcher would obtain a sample comprising the same percentages or proportions, such as 120 females and 80 males in a 200-student subset. Also called proportionate sampling.