2024 – Some researchers claim that herbal supplements such as ginseng or ginkgo biloba

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 μ = 70 and σ = 15. The sample of n = 25 students had a mean score of M = 75. 

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

b.  Compute Cohen’s d for this study.

 

32.A sample of n = 9 participants is obtained from a population with μ = 29, and a treatment is administered to the individuals in the sample. After treatment, the scores for the nine participants are as follows: 23, 33, 26, 28, 30, 26, 27, 25, 25.      

a.  Are the data sufficient to conclude that the treatment has a significant effect? Use a two-tailed test with α = .05.

b.  Are the data sufficient to conclude that the treatment significantly decreased scores? Use a one-tailed test withα = .05.

 

33.The following data are from an independent-measures experiment comparing two treatment conditions:                  Treatment 1     Treatment 2

	6	19
	13	9
	8	18
	4	10
	13	12
	4	14
	11	19
	5	11

a.  Do these data indicate a significant difference between the treatments at the .05 level of significance?

b.  Compute r² to measure the size of the treatment effect.

c.  Write a sentence demonstrating how the outcome of the hypothesis test and the measure of effect size would appear in a research report.

 

34.For the following data from a repeated-measures study:

a. Find the difference scores

b. Calculate M_D and the variance for the difference scores

c.  Calculate the estimated standard error for the mean difference

 

	Subject	Treatment 1	Treatment 2
	A	12	14
	B	6	16
	C	8	10
	D	9	11