Design effect DEFF

A convenient way to evaluate a sampling design is to compare the design variance of an estimator to the design variance from a references sampling scheme of the same (expected) sample size. Usually, simple random sampling without replacement is chosen as reference. For example, for an estimator t_hat of the total T, the ratio of the two design variances is called the design effect and abbreviated to DEFF. In practice, an estimate of the design effect is calculated using the corresponding variance estimators for the sample data set. An estimator of the design effect is thus deffp(s)(t_hat) = v_hatp(s)(t_hat)/v_hatsrs(t_hat), where p(s) refers to the actual sampling design. See page 15 in Lehtonen, R & Pahkinen, E. (2004)

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