(a) You should have an auditable record of your sampling process. That record should cover the following:
(1) A written description of the sampling plan.
(2) A written procedure for your method of selecting a sample at random.
(3) The list of all service units from which you selected a sample at random for each act of sampling. For example, you should have 52 such lists if you did weekly sampling for an entire year.
(4) The random sample.