Some researchers claim that herbal supplements such as ginseng or ginkgo biloba enhance human memory. To test this claim, a researcher selects a sample of n = 25 college students. Each student is given a ginkgo biloba supplement daily for six weeks and then all the participants are given a standardized memory test. For the population, scores on the test are normally distributed with = 70 and = 15. The sample of n = 25 students had a mean score of M = 75. a. Are the data sufficient to suggest that the herb has a significant effect on memory? Use a two-tailed test with = .05. b. Compute Cohen's d for this study.

1) Select the correct hypotheses (enter T for true of F for false for each of the following):

H0: 70 H0: = 70 H0: < 70 H0: 70

2) Find the boundaries of the critical region:

With = .05, boudaries of critical region are

3) Compute Z-scores

The standard error is M =

Z-scores =

4) State your decision (Enter T for true and F for False):

Reject H0 and conclude that the herb has significant effect in enhancing memory.

Fail to reject H0 and conclude that the herb has no significant effect in enhancing memory.

5) Cohen 's d

Cohen d for this study is