Which of the following statements concerning the auditor's use of statisti- cal sampling is correct?

a. An auditor needs to estimate the dollar amount of the standard devia- tien of the population in order to use classical variables sampling.

b. An assumption of monetary-unit sampling is that the underlying accounting population is normally distributed.

c. A classical variables sample needs to be designed with special consider- ations to include negative balances in the sample.

d. The selection of zero balances usually does not require special sample design considerations when using monetary-unit sampling. P-9652