It is always that when solving paired sample T test you compare same data ?
No, in a paired sample t-test, you do not compare the same data. Instead, you compare two sets of related or paired data. The paired data refers to two observations or measurements that are taken from the same individuals or subjects in a before-and-after or matched pairs design.
For example, let's say you want to compare the effectiveness of a new training program on a group of employees. You measure their performance before the training (pre-test) and after the training (post-test) and want to determine if there is a significant difference in their performance. In this case, you would have two sets of data (pre-test scores and post-test scores) for the same individuals.
The paired sample t-test is used to analyze the mean difference between the paired observations and determine if it is statistically significant. It tests whether the mean difference is significantly different from zero, implying a significant change or effect.