A Paired Sample T-Test is a statistical method used to compare two related groups. It assesses whether the means of these groups differ significantly. This test is commonly applied in situations where the same subjects are measured twice, such as before and after a treatment or intervention. The test calculates the differences between paired observations and determines if the average difference is significantly different from zero. It assumes that the differences are normally distributed. Researchers often use this test in fields like psychology, medicine, and education to evaluate the effectiveness of programs or treatments.