A pain-killing drug was tested for efficacy in 50 women who were experiencing uterine cramping pain following childbirth. Twenty-five of the women were randomly allocated to receive the drug, and the remaining remaining 25 received a placebo (inert substance). Capsules of drug or placebo were given before breakfast and again at noon. A pain relief score, based on hourly questioning throughout the day, was computed for each woman. The possible pain relief scores ranged from 0 (no relief) to 56 (complete relief for 8 hours). Summary results are shown in the table.
|
|
PAIN RELIFE SCORE |
| TREATMENT |
n |
MEAN |
SD |
| Drug |
25 |
31.96 |
12.05 |
| Placebo |
25 |
25.32 |
13.78 |
(a) Test for evidence of efficacy using a t test. Use a directional alternative and α = 0.05.
(b) If the alternative hypothesis were nondirectional, how would the answer to part (a) change?