The t-test was developed by William Sealy Gosset in 1908. The objective of this test is to compare the means of two related or unrelated sample groups. It is used in hypothesis testing to test the applicability of an assumption to a population of interest. When you expect a single value hypothesis, like mean1=mean2, a one-tailed test would be preferable. T-Tests are parametric tests for determining correlations between two data to be distributed according to the following assumptions.