Study Design
The t test for independent means requires that there is no overlap between the two groups in the research design. This is what we mean by "independent means". In this design, we collect data from two separate samples. We only use the t test for independent means when we are studying two groups; a different statistic is used when there are more than two groups. In this test, we compare the observed difference between the two sample means (M₁ - M₂) to the expectation that there is no difference in the population
(μ₁ - μ₂ = 0).