One tailed test of hypothesis: difference between means. Do these data provide sufficient evidence to indicate that device A is more effective than device B.
To evaluate the relative merits of two prosthetic devices designed to facilitate manual dexterity, an occupational therapist assigned 21 patients with identical handicaps to wear one or the other of two devices while performing a certain task. 11 patients wore device A and 10 wore device B. The researcher recorded the time each