Hoe groot is de steekproef?*

Abstract

SummaryThe effective size of stratified samples.In this paper, the notion of effective size of a stratified sample is introduced, being defined as the total size of a stratified sample with optimum allocation over the strata that yields an estimate with the same sampling error as the sample concerned. The efficiency is defined as the ratio between the effective sample size and the actual size of the sample. This efficiency is rather low if allocation deviates considerably from the optimum.Furthermore we define the marginal rate of return by the increase in effective sample size divided by the increase in sample size in one or some of the strata in an optimally allocated stratified sample. Finally the substitution rate of return indicates by how many elements the sample size in the remaining strata can be reduced if the effective sample size is to remain unchanged. A practical example is afforded in which the variances in the strata are assumed equal.