Final answer:
Population variability in an audit plan using mean-per-unit statistical sampling is measured by the standard deviation. It quantifies how data points are spread out around the mean and is key for determining sample adequacy and inferences about the population.
Step-by-step explanation:
When evaluating an audit plan that involves mean-per-unit statistical sampling, population variability is a critical measure. This variability, referring to how the sampled data points diverge from each other within the population, is quantified through a specific statistical term. One commonly used measure is the standard deviation of the population, which assesses how spread out the values are around the mean (average) of the population.
The population variability is not gauged by the sample mean or the difference between the estimated population total and the actual population total. Instead, it is measured by the standard deviation within the population. The standard deviation is particularly valuable because it accounts for the dispersion of all data points relative to the mean, thus providing a holistic view of variability.
In the context of statistical sampling in audits, understanding and accurately calculating the standard deviation enables auditors to evaluate the precision and reliability of the sample mean as an estimator of the population mean. It is crucial for auditors to measure this variability to determine the adequacy of the sample size and to make informed inferences about the population based on the sample data.