Final answer:
To gather evidence around the risk of making a purchase from an unauthorized vendor, auditors should open and join the Accounts_Payable and Vendors databases for Roger Company, using vendor number as the matching criteria. Retain all records in both files and determine the total number of records in the joint database.
Step-by-step explanation:
To gather evidence around the risk of making a purchase from an unauthorized vendor, auditors can open and join the Accounts_Payable and Vendors databases for Roger Company. Firstly, open the Accounts_Payable file and go to the Analysis tab. Then, in the Relate group, select Join to open the Join Databases window. Choose Vendors as the Secondary database and join both databases by vendor number in the Match menu. Retain all records in both files and determine the total number of records in the joint database.