(Not from a book and do all BY HAND! ! !) Many people taking ginkgo supplements advertised to improve memory. Are these over-the-counter supplements effective? In a study reported in the paper "Ginkgo for Memory Enhancement" ( Journal of the American Medical Association [ 2002]:835-840), elderly adults were assigned at random to either a treatment group or a control group. The 104 participants who were assigned to the treatment group tool 40 mg of ginkgo three times a day for six weeks. The 115 participants assigned to the control group took a placebo pill three times a day for six weeks. At the end of six weeks, the Wechsler Memory Scale (a test of short-term memory) was administered. Higher scores indicate better memory function. Summary values are given in the following table. n y-bar S 1=Ginkgo 104 5.6 .4 2=Placebo 115 5.4 .5 Based on these results, is there evidence that taking 40mg of ginkgo three times a day is effective in increasing mean performance on the Wechsler Memory Scale? (use alpha=0.05) a. Is this an observational or experimental study? Explain. b. Identify the explanatory and response variables. c. Define the parameter of interest d. State the Null and Alternative Hypothesis