## EXAMPLE 1 (from Levy and Lemeshow p 292):
## We intend to conduct a survey of nurse practitioners to estimate the
## average number of patients seen by each nurse. There are five health
## centres in the study area, each with three nurses. We intend to sample
## two nurses from each health centre. We would like to be 95% confident
## that our estimate is within 30% of the true population value. We expect
## that the mean number of patients seen at the health centre level
## is 84 (var 567) and the mean number of patients seen at the nurse
## level is 28 (var 160). Previous studies report an intracluster
## correlation for the number of patients seen per nurse to be 0.02.
## How many health centres should be sampled?
epi.ssclus2estc(N.psu = 5, N.ssu = 15, b = 2, xbar = 28, xsigma = sqrt(160),
epsilon = 0.30, error = "relative", rho = 0.02, nfractional = FALSE,
conf.level = 0.95)
## A total of 3 health centres need to be sampled to meet the specifications
## of this study.
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