A nutrition store in the mall is selling "Memory Booster," which is a concoction of herbs and minerals that is intended to improve memory performance. To test the effectiveness of the herbal mix, a researcher obtains a sample of n = 16 people and asks each person to take the suggested dosage each day for four weeks. At the end of the four-week period, each individual takes a standardized memory test. The scores from the sample produce a mean of M = 26 with SS = 960. In the general population, the standardized test is known to have a mean of μ = 20. a. Do the sample data support the conclusion that the Memory Booster has a significant effect? Test with α = .05. b. Compute Cohen's d to measure the size of the treatment effect.
NOTE: Please explain if the hypothesis is directional and if a one-tailed or a two-tailed a should be used. Thank you!