Question

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 = 36 college students. Each student is given a ginkgo biloba supplement daily for six weeks, and then all the participants are given a standardized memory task. For the population, scores on the test are normally distributed with µ = 70. The sample of n = 36 students had a mean score of M = 75 and a standard deviation of s = 10. Can we conclude that the herb has a significant effect on memory? Use a two-tailed test with α = 0.01.

What type of statistical test is appropriate for this research question?

State the null and alternative hypotheses using statistical notation OR using plain English (a sentence for each)

What are the degrees of freedom and critical values for this test?

Calculate the test statistic

What is your decision? And what does that decision mean, or how would you interpret/explain your decision?

Compute Cohen’s d. How would you describe the size of the effect

Answer 1

(a)

Question:

What type of statistical test is appropriate for this research question?

One Sample t test

(b)

State the null and alternative hypotheses using statistical notation OR using plain English (a sentence for each)

H0: Null Hypothesis: =70 ( Herbal supplements such as ginseng or ginkgo biloba do not enhance human memory. )

HA:Alternative Hypothesis: 70 ( Herbal supplements such as ginseng or ginkgo biloba enhance human memory. ) (Claim)

(c)

Qustion:

What are the degrees of freedom and critical values for this test?

(i)

the degrees of freedom = 36 - 1 = 35

(ii)

= 0.01

From Table, critical valuesof t = 2.724

(d)

Question:

Calculate the test statistic

Test Statistic is given by:

(e)

Question:

What is your decision? And what does that decision mean, or how would you interpret/explain your decision?

Since calculated value of t = 3.00 is greater than critical value of t = 2.724, the difference is significant. rejectnull hypothesis.

Conclusion:
The data support the claim that Herbal supplements such as ginseng or ginkgo biloba enhance human memory.

(f)

Cohen's d is given by:

Since Cohen's d value = 0.5, we conclude:

Effect size is medium.