A sampling fraction, denoted f, is the proportion of a universe that is selected for a sample. The sampling fraction is important for survey estimation because in sampling without replacement, the sample variance is reduced by a factor of (1 − f), called the. finite population correction or adjustment.

In a simple survey design, if a sample of n is selected with equal probability from a universe of N, then the sampling fraction is defined as f = n/N. In this case, the sampling fraction is equal to the probability of selection. In the case of systematic sampling, f = 1/i where i is the sampling interval.

The sampling fraction can also be computed for stratified and multi-stage samples. In a stratified (single-stage) sample, the sampling ...