A crossover trial is a type of experiment used to compare two drugs. Subjects take one drug for a period of time, then switch to the other. The responses of the subjects are then compared using matched pair methods. In an experiment to compare two pain relievers, seven subjects took one pain reliever for two weeks, then switched to the other. They rated their pain level from 1 to 10, with larger numbers representing higher levels of pain. The results were

Can you conclude that the mean response differs between the two drugs?

Subject 1 2 3 4 5 6 7 5 7 1 4 5 5 2 Drug A 6 3 4 Drug B 5 1 5 2