A complex sample may be multistage, stratified, or clustered.
Many samples also have unequal probabilities of selection, or are drawn from finite populations.
Contact your TC to request installation. Most commonly used statistical packages do not account for complex sample designs when computing variance estimates and test statistics. Numerical accuracy Checks are built into the system to ensure that definitions are meaningful and that computations are feasible. In the pharmaceutical and epidemiological sciences, researchers often encounter data observed in clusters. Data must be sorted according to stages of sample selection as specified on the NEST statement.