W]hen a survey is based on probability sampling, the probabilities or risks of sampling misstatements of various sizes can be calculated.

If files are computerized and 100% verification cannot be performed by computer-assisted audit techniques, then probability sampling is most likely to be the practical approach.

Multistage national probability sampling through providers supplies uniquely valuable information, but will not represent populations not receiving medical care and may not provide sufficient cases in subpopulations of interest.

Multistage probability sampling through providers can provide unbiased, nationally representative data on persons receiving regular medical care for uncommon diseases and can improve our ability to accurately study care and its outcomes for diseases such as HIV/AIDS.

In our companion article, we discussed the fact that national

probability sampling is the sampling method of choice for many studies because it can produce a representative sample and yield unbiased answers to key questions (Shapiro, Berk, Berry, et al.