A two-sample t-test is a statistical test compares the means of two independent groups to determine if they are significantly different. It assumes that the two groups are unrelated, the data in each group are approximately normally distributed, and that the variances are equal (or uses a modified version if variances are unequal). Researchers often use the two-sample t-test when comparing outcomes between two different treatments, groups, or populations. This test is also known as an independent samples t-test.
For example, a study might use a two-sample t-test to compare the average test scores of students who took two different versions of a preparation course. One group might have used an online course, while the other attended in-person classes. The test will determine whether any observed difference in average scores is statistically significant.