Equal Probability of Selection

Survey samples can be chosen in many ways, and one common approach is to use a technique that provides an equal chance of selection to all elements in the sampling frame. One type of equal probability sample is a simple random sample, but there are many others.

Morris H. Hansen, William N. Hurwitz, and William G. Madow appear to have been the first to refer to them as EPSEM samples (“equal probability selection method”), but the term was so often used by Leslie Kish that some have misattributed the coinage to him. Others have used the phrase self-weighting sample, although some eschew this term, given that weighting typically involves nonresponse adjustment and some form of calibration such as ratio adjustment or raking, and these lead to ...