Question: The herbal supplement ginkgo biloba is advertised as producing an increase in physical strength and stamina. To test this claim, a sample of n =36 adults is obtained and each person is instructed to take the regular daily dose of the herb for a period of 30 days. At the end of the 30-day period, each person is tested on a standard treadmill task for which the average, age-adjusted score is m = 55. The individuals in the sample produce a mean score of M = 58.5 with SS = 5040.

a. Are these data sufficient to conclude that the herb has a statistically significant effect using a two-tailed test with a = .05?

b. What decision would be made if the researcher used a one-tailed test with a = .05? (Assume that the herb is expected to increase scores.)