In a paired sample t-test, what are being compared?

In a paired sample t-test, the focus is on comparing means from the same group measured under different conditions or at two different time points. This statistical method is used when you have two related samples, such as pre-test and post-test measurements for the same subjects. The purpose of the paired sample t-test is to determine whether there are statistically significant differences between these two related means, which helps to analyze the effect of an intervention or change over time on the same participants.

This testing approach is particularly advantageous because it controls for individual differences across the samples by analyzing the differences within the same subjects. Consequently, the paired sample t-test increases the statistical power of the test as compared to unpaired tests since it reduces variability due to individual differences.

Other answer choices relate to different concepts in statistical analysis. While independent groups require unpaired tests, such as an independent samples t-test, and variations in influences of independent variables typically pertain to more complex analyses like ANOVA, the paired sample t-test is specifically about means from the same group, making the correct answer clear in the context of paired sample comparisons.