Representative sampling is a form of statistical sampling in which a researcher tries to choose a small group of subjects who have the qualities of a larger population. A researcher will gather data from a small group and try to use that data to draw conclusions about the larger population.
To obtain a representative sample, the researcher needs to define the larger population.
A research team wants to study the academic performance of incoming freshmen who were home-schooled in the US. They find that 40% of this larger population is female, and 60% is male.
A representative sample would then need to be 40% female and 60% male.
A researcher might also consider variables like location, income level, age, and ethnicity when selecting human subjects. By narrowing down the definition of the larger population, researchers can reduce the number of variables involved.
(e.g. the number of home-schooled freshmen at one university vs. the number of home-schooled freshmen enrolled in any college.)