EPSEM samples are probability samples where each observation in the population has the same known probability of being selected into the sample (EPSEM stands for equal probability of selection method sampling; see Kish, 1965, for a comprehensive discussion of sampling techniques).

EPSEM samples have certain desirable properties; for example, the simple formulas for computing means, standard deviations, etc., can be applied to estimate the respective parameters in the population. In STATISTICA, you can create EPSEM samples by using the Random Sampling options, which also support Stratified Random Sampling.