In order for the results of a paired difference experiment to be unbiased, the experimental units in
each pair must be chosen independently of one another.

Question

Quizplus · Accepted Answer

In a paired difference experiment, the experimental units in each pair are not chosen independently; rather, they are intentionally paired because they are similar in some way that is important to the experiment, which helps to control for confounding variables and reduce variability in the comparison of the treatment effects.

In Order for the Results of a Paired Difference Experiment