Exact Tests

Exact tests are hypothesis tests that are guaranteed to produce Type-I error at or below the nominal alpha level of the test when conducted on samples drawn from a null model. For example, a test conducted at the 5% level of significance that yields (false) “significant” results 5% of the time or less (when used on samples drawn from a null model) is exact. See also permutation tests, which constitute the largest class of exact tests.