library(survey) data(api) ## one-stage cluster sample dclus1<-svydesign(id=~dnum, weights=~pw, data=apiclus1, fpc=~fpc) # svyglm model mod <- svyglm(api99 ~ enroll + api.stu, design = dclus1, deff = TRUE) #deffs returned from svyglm model - implausibly high deff(mod) #> (Intercept) enroll api.stu #> 351.3500 457.6799 491.5567 # run mod with same data and glm() srs_mod <- glm(api99 ~ enroll + api.stu, data = apiclus1) # manually calculate deffs clust_se <- summary(mod)$coefficients[,2] srs_se <- summary(srs_mod)$coefficients[,2] deffs <- clust_se^2 / srs_se^2 stopifnot(all.equal(deffs, deff(mod)))
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