The total population size is traditionally labeled N, as opposed to the sample size, which is termed n. The population size N refers to the total number of elements in the population, target population, or universe.

N also refers to the number of elements on the sampling frame from which the sample is to be drawn. Since in many cases, the list of population elements contains foreign elements, the accurate number of eligible population elements is less than the number of elements on the list. In other cases, the population list not only contains foreign elements but also contains omissions and inaccuracies. These further put into question the validity of the value of N, which should be assessed carefully both before and after sample selection and ...