Although there is a popular belief that herbal remedies such as Ginkgo biloba and Ginseng may improve learning and memory in healthy adults, these effects are usually not supported by well-controlled research (Persson, Bringlov, Nilsson, and Nyberg, 2004). In a study, a researcher obtains a sample of n = 16 participants and has each person take the herbal supplements every day for 90 days. At the end of the 90 days, each person takes a standardized memory test. For the general population, scores from the test form a normal distribution with a mean of μ = 50 and a standard deviation of σ = 12. The sample of research participants had an average of M = 54. Using the standard 4-step procedure, conduct a two-tailed hypothesis test with a .05 level of significance, α = .05, and p = .059 to evaluate the effect of the supplements.
o Step 1: State the hypotheses. State the null hypothesis and the alternative hypothesis. Write the hypotheses using statistical notation and for each, include a statement of interpretation in plain English.
o Step 2: Set the criteria for a decision. State the level of significance, the alpha level, and whether the test is one-tailed (directional) or two-tailed (nondirectional).
o Step 3: Compute the test statistic. State the observed p value.
o Step 4: Make a decision. State whether to retain or reject the null hypothesis.
We do not do your homework for you. Although it might take more effort to do the work on your own, you will profit more from your effort. We will be happy to evaluate your work though.
I will start you out. State with your own notations.
Ho: no difference
Z = (mean1 - mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√n
If only one SD is provided, you can use just that to determine SEdiff.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability of the Z score to compare to your level of significance.
posted by PsyDAG