A two samples t-test is used when you’re looking at a numerical variable – for example, height – and then comparing the averages of two separate populations or groups. In order to conduct a two samples t-test, several conditions must be met. For one, the two samples must be independent of one another. This means that observations in one group cannot also be part of the other group. For another, the data should be normally distributed. In addition, the two samples should not have the same variance.
Here is an example of a two samples t-test.