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 typical 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

Question

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 typical 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 s.d=12 . The sample of research participants had an average of M=54 .

a)Assuming a two-tailed test, state the null hypothesis in a sentence that includes the two variables being examined.

b)Using the standard 4-step procedure, conduct a two-tailed hypothesis test with alpha=.05 to evaluate the effect of the supplements.

PsyDAG · Answer

What "two variables"? I only see the memory test.

Z = (score-mean)/SEm

SEm = SD/√n

Look in the back of your statistics textbook for a table called something like “area under normal distribution” to find the proportion/probability related to the Z score.