Definition

A summary statistic (or a function of a summary statistic) computed from the sample, that is used to make a decision on whether or not to reject the null hypothesis. The actual form of the test statistic will depend on the parameter and the type of hypothesis being tested.

The test statistic value is compared with its distribution under the null hypothesis in order to see how likely it is to have taken that particular value under the terms of the null hypothesis. If this chance (the p-value) is small, we reject the null; otherwise, we fail to reject it.