A crossover trial is a type of experiment used to compare two drugs. Subject 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 large numbers representing higher levels of pain. The results were Subject 1 2 3 4 5 6 7 Drug A 6 3 4 5 7 1 4 Drug B 5 1 5 5 5 2 2 (a) Find a 95% confidence level for the difference of mean responses between the two drugs?