For example, if we are studying Scabies incidence in a sample of school children, all the school children comprise our reference population. It is the population to which, we apply or extrapolate the end results or inferences obtained after testing our hypothesis.

These populations may be as narrow and small as exposed groups or as big and universal as for example, all reproductive women.

It usually serves as denominator to calculate rates and ratios to quantify the disease/exposure load.