Outlined below are some audit tasks performed by an audit assistant:

1. Opened the file of purchase invoices and selected 20 orders as part of tests of controls over occurrence.

2. Performed proof-in-total calculations in relation to the depreciation charge for the year.

3. Discussed with management the contents of the board minutes in relation to the approval of large projects.

4. Selected all large and unusual payments appearing in the bank nominal ledger account.

5. Selected 10 payments made during the year for substantive testing.

6. Selected all material receivables balances for receivables circularisation tests.

7. Selected every hundredth sales invoice and checked to goods despatched note.

8. For a company with a chain of retail shops, calculated the gross profit for each shop for reasonableness checks against prior years and budget.

Required

a. Are each of the above audit sampling techniques?

b. If not, are they acceptable audit procedures? Discuss.

c. If yes, are they random selection methods? Discuss.