A t-test is a statistical hypothesis test in which the test statistic obeys a Student's t-distribution under the null hypothesis. It can be used to test whether two datasets are significantly different from each other. A t-test is mostly applied when the values of a scaling term in the test statistic are known and follow a random distribution pattern. When the scaling term is unknown and is replaced by an estimate according to the data, the test statistics (under some conditions) follow a Student's t distribution.