How do you test whether or not there is a difference between treatments A, B, and C, a sample of 12 observations has been randomly assigned to the 3 treatments. You are given the results below.

Treatment Observation

A 20 30 25 33

B 22 26 20 28

C 40 30 28 22

The null hypothesis is to be tested at the 1% level of significance. In order to determine if I can accept or reject the null hypothesis I need to find the p-value. I know how to compare 2 observations, but not 3.