A statistical sampling method for selecting elements from a population in such a way that every element within that population has the same probability of being selected. This is not an exact definition however, so here is a statistician's definition: In simple random sampling, we select a sample n out of N population units such that each subset of size n has the same probability of occurring.  For example, if population size is N = 100, and sample size is n = 10, then each random sample of size 10 has probability 1/(100 choose 10) of occurring.  Many misinterpret simple random sampling to mean that each unit has probability n/N of being in the sample; however, many sampling procedures that are not simple random sampling have this property.