In any given scenario, Discovery sampling is used when objective of audit is to discover fraud or other irregularities.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-sampling is used when auditor believes that very few errors will be found. It prevents excessive sampling by allowing an audit test to be stopped at the earliest possible moment. Attribute sampling method (either control is present or absent) will be useful when testing for compliance. Variable sampling is generally used for substantive testing.