d. Monetary-unit sampling (Mus), also known as probability-proportional-to-size (PPS) sampling, uses a monetary unit the sampling unit. It applies attribute sampling methods to reach conclusion about the probability of overstating monetary amounts.
1) Under MUS, the sampling unit is a unit of money rather than, for example, an invoice or an account balance. The item (invoice, account, etc.) containing the sampled monetary unit is selected for testing.
2) MUS is appropriate for testing account balances for overstatement when some item may be far larger than others in the population. In effect, it stratifies the population because the larger account balances have a greater chance of being selected.
3) MUS is most useful if few misstatements are expected.
4) MUS does not require the use of a measure of variability (e.g., standard deviation) to determine the sample size or interpret the results.
5) Thus, in the example on the previous page, the objective of MUS may be to determine that the total recorded amount of accounts receivable (US $3,500,000) is not overstated by more than 3%, with a confidence level of 95%.