Mean-per-unit (MPU) estimation is a classical variable sampling technique used to estimate the total audited value of a population by applying the average audited value per unit from the sample to the total number of units in the population. Unlike ratio or difference estimation, MPU does not consider book values in projection, making it especially useful when book values are unreliable or inconsistent.

To use this method, the auditor calculates the average audited value per account in the sample and multiplies it by the total number of accounts in the population. The result provides an estimate of the population’s total audited value, which can then be compared to the book value to assess potential misstatements.

Practical Example:
An auditor reviews 500 accounts with a total audited value of $600,000. This gives an average audited value per account of:

600,000/ 500=1,200

The population contains 6,200 accounts, so the projected audited value is:

6,200×1,200=7,440,0006,200 

The book value of the population is $7,120,000, resulting in a projected understatement of $320,000.

This method suggests the population may be materially understated, prompting further investigation. MPU is most appropriate when every sampling unit is of similar size and importance.