Suppose we do an experiment with 4 subjects. Two subjects are randomly assigned to treatment A. The other 2 receive treatment B. The response variable is number right on a 10 point quiz. The subjects that received treatment A had scores of 7 and 5 on the quiz. The subjects that received treatment B had scores of 3 and 1 on the quiz. Compute a 2-sided p-value for testing for a difference between treatment A and treatment B. Original Data: A B Difference in Means 7 5 3 1 4 All possible assignments of subjects to treatments: A B Difference in Means 7 5 3 1 4 7 3 5 1 2 7 1 5 3 0 3 1 7 5 -4 5 1 7 3 -2 5 3 7 1 0 2-sided p-value is 2/6 or about 0.333 because 2 of the 6 possible assignments of subjects to treatments have a difference as far from 0 as the difference observed in the original data. There is no convincing evidence that one treatment is better than the other because it would not be too unusual (2 out of 6 chance) to see results as extreme as those we obtained even if the treatment has no effect on the quiz scores.