You are the staff auditor testing the combined purchase and cash disbursements journal for a small audit client. Internal control is regarded as reasonably effective, considering the number of personnel.

The in-charge auditor has decided that a sample of 80 items should be sufficient for this audit because of the excel¬ lent controls and gives you the following instructions:

1. All transactions selected must exceed $100.

2. At least 50 of the transactions must be for purchases of raw material because these transactions are typically material.

3. It is not acceptable to include the same vendor in the sample more than once.

4. All vendors' invoices that cannot be located must be replaced with a new sample item.

5. Both cheques and supporting documents are to be examined for the same transactions.

6. The sample must be random, after modifications for instructions 1 through 5.

Required

a. Evaluate each of these instructions for testing acquisition and cash disbursements transactions.

b. Explain the difficulties of applying each of these instructions to attributes sampling.