The most elementary methodology is called [Simple Random Sampling]?. Most of the theory of statistics assumes this kind of sampling unless otherwise noted. It assures that every possible subset of the population which has the desired sample size is given the same probability of selection. The possibility of very expensive or very atypical samples has lead to a variety of modfications such as stratified sampling, cluster sampling, and [multistage sampling]?. The most experienced center in these techniques outside the Census Bureau is the [University of Michigan Survey Research Center]?.
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