Final answer:
The auditor is performing a test on the file of shipping documents to determine whether invoices were prepared. This test is conducted to assess the assertion of completeness.
Step-by-step explanation:
The auditor is performing a test on the file of shipping documents to determine whether invoices were prepared. This test is conducted to assess the assertion of completeness.
Completeness is one of the four assertions in auditing, which refers to the inclusion of all transactions and events that should have been recorded in the financial statements.
By selecting a sample from the shipping documents, the auditor is checking if all the transactions involving the preparation of invoices have been properly recorded. If invoices were not prepared for certain shipments, it could indicate a potential omission or error in the financial statements.