Design Effects (deff)

The design effect (deff) is a survey statistic computed as the quotient of the variability in the parameter estimate of interest resulting from the sampling design and the variability in the estimate that would be obtained from a simple random sample of the same size.

In large-scale sample surveys, inferences are usually based on the standard randomization principle of survey sampling. Under such an approach, the responses are treated as fixed, and the randomness is assumed to come solely from the probability mechanism that generates the sample. For example, in simple random sampling without replacement, the sample mean is unbiased with randomization-based variance given by

where n, N, and f = n/N denote the sample size, the population size, and the sampling fraction, respectively, and S2 is ...