Discovery sampling is used when an auditor is trying to determine whether a type of event has occurred, and therefore it is suited to assess the risk of fraud and to identify whether a single occurrence has taken place. Stop-or-go is a sampling method that helps limit the size of a sample and allows the test to be stopped at the earliest possible moment. Classical variable sampling is associated with dollar amounts. Probability-proportional-to-size sampling is typically associated with cluster sampling when there are groups within a sample. The question does not indicate that an IS auditor is searching for a threshold of fraud.