Consider again the conditions of Exercise 1. Discuss how the design of this experiment might be improved by considering how the 20 men who participate might be selected and also by considering the possible effect of having each man shave first with a blade of type B and then with a blade of type A.
Exercise 1
In an experiment to compare two different types of long-lasting razor blades, A and B, 20 men were asked to shave with a blade of type A for one week and then with a blade of type B for one week. At the end of this period, 15 men thought that blade A gave a smoother shave than blade B. and the other 5 men thought that blade B gave a smoother shave. Test the null hypothesis that blade A does not tend to give a smoother shave than blade B against the alternative that blade A tends to give a smoother shave than blade B.