A clinical psychologist wants to choose between two therapies for treating mental depression. For six patients, she randomly selects three to receive therapy A, and the other three receive therapy B. She selects small samples for ethical reasons; if her experiment indicates that one therapy is superior, that therapy will be used on her other patients having these symptoms. After one month of treatment, the improvement is measured by the change in score on a standardized scale of men- tal depression severity. The improvement scores are 10, 20, 30 for the patients receiving therapy A, and 30, 45, 45 for the patients receiving ther- apy B.

(a) Lising the method that assumes a common?