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 ? = 50 and a standard deviation of o = 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.