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.

Are the data sufficient to that the herb has a significant effect on memory? Use a two-tailed test with = .05.

Compute Cohen's d for this study.

1. What are the Hypotheses: H_o & H₁?

a. u=75, u not =75

b. u=70, u not=70

c. u=12, u not=12

d. u=36, u not=36

2. What is the Z_crit value for this study?

a. 3.58

b. 2.65

c. 1.75

d. 1.96

3. What is the standard error for this study?

a. 3

b. 2

c. 6

d. 4

4. What is the Zobtained value for this study?

a. 1.67

b. 1.96

c. 1.25

d. 2.50

5. what is the correct decision for this study?

a. Accept Ho/ Fail to reject Ho

b. Reject H1

c. Reject Ho

d. Accept H1

6. Compute Cohen's d for this study

a. 0.53

b. 1.67

c. 0.33

d. 0.23

A sample of students is selected from a population with= 50. After treatment is administered to the individuals in the sample, the mean is found to be M = 55 and the variance is s²= 64.

If the sample hasn= 16 scores, then conduct a hypothesis test to evaluate the significance of the treatment effect.

7. Hypotheses: Ho & H1?

a. u=64, u not =64

b. u=55, u not=55

c. u=70, u not=70

d. u=50, not = 50

8. What is the df?

a. 15

b. 13

c. 14

d. 16

9. What is the tcrit value?

a. 1.96

b. 1.65

c. 2.306

d. 2.131

10. What is the est. standard error or est. s.e. value?

a. 4

b. 6

c. 3

d. 2

11. What is the tobt value?

a. 1.25

b. 1.96

c. 1.67

d. 2.50

12. What is the correct decision for this study?

a. reject Ho

b. Accept H1

c. Accept Ho / Fail to Reject Ho

d. Reject H1

13. Calculate Cohen's d to measure the size of the treatment effect. (you can round your answer)

a. 1.67

b. 0.23

c. 0.33

d. 063