What is monetary unit sampling (MUS) and when is it used?

MUS (probability-proportional-to-size) selects sampling units as individual monetary units, so larger-value items have a higher chance of selection. It's efficient for detecting overstatement in populations with few large errors (e.g., receivables, inventory), automatically emphasizing high-value items, and provides a statistical projection of misstatement. It's less suited to testing understatement or populations with many small errors.

Sampling interval = Tolerable misstatement / reliability factor
Every n-th monetary unit is selected (large items sampled more).