Many people take ginkgo supplements advertised to improve memory. Are these over-the-counter supplements effective? In a study reported in the paper €œGinkgo 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 took 40 mg of ginkgo three times a day for 6 weeks. The 115 participants assigned to the control group took a placebo pill three times a day for 6 weeks. At the end of 6 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.

Based on these results, is there evidence that taking 40 mg of ginkgo three times a day is effective in increasing mean performance on the Wechsler Memory Scale? Test the relevant hypotheses using a = .05.

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Ginkgo 104 5.6 Placebo 15 5.5 6 6