Robust estimation in finite populations II: Stratification on a size variable

It has been established in Part I [3] that for estimating a finite population total, the estimators which are optimal under simple super-population models can be made insensitive to certain departures from the models by the choice of balanced samples. Here stratification on a size variable is considered as another technique for protecting against model failure. Together the two techniques, stratification and balanced sampling, are shown to provide more efficient protection than does balanced sampling alone. Questions of definition of strata and of allocation of sampling units among strata are also considered.