Final answer:
Auditors most frequently use tests of control sampling during their study of internal control. One common type of non-random sampling is convenience sampling, which relies on readily available results and can potentially lead to biased outcomes.
Step-by-step explanation:
The type of sampling most frequently used by auditors during their study of internal control is known as the test of controls. This sampling approach focuses on the internal controls and procedures that a company has in place to maintain financial integrity and compliance with accounting standards. Auditors may use a variety of sampling techniques, with one common non-random method being convenience sampling. Convenience sampling involves using results that are readily available, such as reviewing transactions that occurred during a specific time frame or at a certain location within the company. While this method can produce good results, it may also lead to biased outcomes that are not representative of the entire population or situation. In the context of auditing, using convenience sampling might provide insight into the functioning of internal controls, but auditors must be wary of relying exclusively on this method, as it does not provide a random or comprehensive sample of the control environment.