There isn't a single specific notation or symbol used for "exact tests" in general. The term "exact test" simply refers to a type of hypothesis test where the distribution of the test statistic is calculated exactly, rather than using an approximation. This is often done when sample sizes are small or when the assumptions of other tests are not met.

However, specific exact tests do have their own notation and symbols. For example:

* Fisher's exact test: This test is often represented by the symbol "Fisher's exact test" itself or sometimes "FET".

* Binomial test: This test might be denoted by "B" or "Binomial test".

* Permutation test: This test might be denoted by "Permutation test" or "P-test".

It's important to note that the specific notation used for exact tests might vary depending on the context and the specific field of study. The most important thing is to clearly state which exact test is being used and to provide enough information for the reader to understand how it was conducted.