15.26 A pharmacist randomly selected a group of 45 individuals with a similar level of back pain. The participants randomly distributed into three treatment groups in which using three different medicines (M1, M2 and M3)

to treat their back pain for a period of one month. During the treatment, the daily amounts of the medicines taken by the participants are recorded. The pharmacist wants to compare the levels of pain experienced by the different groups at the end of the treatment.

a. What test is suitable for the pharmacist to achieve his goal? Why?

b. Give two assumptions for conducting the suggest test.