Unit 2, Question 5

What is the probability of randomly selecting a sample from the population whose mean falls between M = 38 and M = 62 on the memory test?

a. Approximately 68%

b. Approximately 95%

c. Approximately 99.7%

d. Not enough information to determine

Scenario:

Although there is a popular belief that herbal remedies such as Gingko biloba and Ginseng may improve learning and memory in healthy adults, these effects are usually not supported by well-controlled research (Persson, Bringlov, Nilsson, & Nyberg, 2004). In a recent study, a researcher obtained a sample ofn = 16 participants and had each person take the herbal supplement every day for 90 days. At the end of the 90 days, each person took a standardized memory test. For the general population, the scores on this memory test form a normal distribution with a = 50 and = 12. The sample of research participants had an average score of M = 54.