Independent t-test and paired t-test

An Independent Samples t-test compares the means for two groups. A Paired sample t-test compares means from the same group at different times.

The independent t-test test the difference between a variable (such as income) between two groups. Meanwhile the paired t-test test the difference between two variables (such as the husband’s income and the wife’s income) for all the cases. Besides, the paired t-test can be used for comparing the difference of a variable at pre-test and post-test.