When testing the accuracy of transaction data, which of the following situations BEST justifies the use of a smaller sample size?

Proper separation of duties is a control strength, but by itself, it does not guarantee transaction data accuracy enough to significantly reduce sample size without further testing or strong historical evidence of accuracy.

The experience of the audit staff may improve the efficiency of testing but does not change the statistical requirements for sample size based on population characteristics or control effectiveness.

If data can be directly changed by users, it increases the risk of error or manipulation, which would typically necessitate a larger, not smaller, sample size for accuracy testing.

If the IS auditor expects the population to be error-free or to have a very low error rate, this implies a low inherent risk or strong internal controls are in place, which reduces the need for extensive testing and thus allows for a smaller sample size while still providing sufficient assurance. The auditor's confidence in the population's quality directly influences the required sample size.