Jamila, an auditor, is informed that all purchase orders $($POs$)$ must be approved by Anita, the Purchasing Manager. During the year, $500$ POs were issued. Jamila requests a copy of Anita's signature and checks a sample of $50$ POs to confirm if they were approved by Anita. She keeps count of all the POs that were not approved by Anita with the intention of projecting the deviation rate to the other $450$ POs. What type of test is Jamila performing?

test of details$$focus on transactions

test of details$$focus on balances

substantive analytical procedure

test of controls