Click here to purchase the entire book in PDF format. Paired comparisons In a paired comparison, the subject is presented with two stimuli and is asked to rate how one compares to the other. For example, you are given two cups of coffee, ``Cup A'' and ``Cup B'' and you are asked ``Which of the two cups of coffee is sweetest?'' (or hottest, or most bitter, or ``Which cup of coffee do you prefer?'') In this case, you're comparing a pair of stimuli. There is no real reference, each of the two stimuli in the pair is referenced to the other. The nice thing about this test is that you can design it to check your answers. For example, let's say that you have 3 cups of coffee to test in total (A, B, and C), and you do a paired comparison test (so you ask the subject to compare the sweetness of A and B, then B and C, then A and C). Let's also say that A was rated sweeter than B, and B was rated sweeter than C. It should therefore follow that A will be rated sweeter than C. If it isn't, then the subject is confused, or lying, or just not paying attention, or doesn't understand the question, or the differences in sweetness are imperceptible. The good thing is that you can check the subjects' answers if the test is properly designed and includes all possible pairs within your set of all stimuli.