In what type of test is the variable of interest the difference between the values of the observations rath?

1. In what type of test is the variable of interest the difference between the values of the observations rather than the observations themselves?


a. A test for the equality of variances from two independent populations.


b. A test for the difference between the means of two related populations.


c. A test for the difference between the means of two independent populations.


d. All of the above.

In what type of test is the variable of interest the difference between the values of the observations rath?
b. This is called a paired t-test, or z-test, depending on sample size. The variable is not the actual measurements, but the difference between a before-and-after measurement on the same or related populations.