12.14 An experimenter is attempting to evaluate the relative effectiveness of four drugs in reducing the pain and trauma of persons suffering from migraine headaches. Seven patients are given each drug for a month at a time. At the end of each month, each patient gave an estimate of the relative degree of pain suffered from migraines during that month on a scale from 0 to 10, with 10 denoting the most severe pain. Test the null hypothesis that the drugs are equally effective.

Drug 1 2 3 4 5 6 7 A 7 10 7 9 8 8 8 B 7 6 5 8 7 5 7 C 3 7 3 5 4 6 3 D 4 3 2 1 0 1 0