An internal auditor is conducting tests to determine if an organization is in compliance with its payment approval policies. After reviewing a sample of vouchers selected, the internal auditor concluded that there were indicators of fraud. Which of the following would be the most appropriate method to expand the audit test to achieve the audit objective?
I. Validate the completeness of the accounts payable files.
II. Examine the sample of vouchers in greater detail.
III. Increase the number of vouchers in the sample.
IV. Broaden the scope of the examination to include credits received by accounts payable.