Under Which of the Following Conditions Can the Population Mean

Multiple Choice

Under which of the following conditions can the population mean be estimated without error employing a stratified sample?

A) When the population is partitioned so that the number of elements in each stratum is proportional to size of the sample to be taken from each stratum.
B) When the population is partitioned so that the elements in each stratum are equal.
C) When the population is partitioned in such a way that the variances within strata are equal.
D) When the population is partitioned so that the elements in each stratum are normally distributed.
E) None of these are correct.