ABSTRACT
Stratified simple random sampling is illustrated with Voorst. Tibble grdVoorst with simulated data contains variable stratum. The strata are combinations of soil class and land use, obtained by overlaying a soil map and a land use map. To select a stratified simple random sample, one can set the total sample size n. The stratified simple random sample is selected with function strata of package sampling. The sampling variance of the estimator of the population mean is estimated by first estimating the sampling variances of the estimated stratum means, followed by computing the weighted average of the estimated sampling variances of the estimated stratum means. The estimated proportions, or cumulative frequencies, are used to estimate a quantile. These estimates are easily obtained with function svyquantile of package survey. Using the quantitative variables one-by-one in cum-root-f stratification, followed by overlaying the maps with univariate strata, may lead to numerous cross-classification strata.
