Resveratrol, a compound in grapes and red wine, has been shown to promote weight loss in rodents and now in a primate.10 Lemurs fed a resveratrol supplement for four weeks had decreased food intake, increased metabolic rate, and a reduction in seasonal body mass gain compared to a control group. Suppose a hypothetical study is done for a different primate species, with one group given a resveratrol supplement and the other group given a placebo. We wish to see if there is evidence that resveratrol increases the mean metabolism rate for this species. (This exercise presents hypothetical data. We will see the results from the actual study later in this chapter.) (a) Define the relevant parameter(s) and state the null and alternative hypotheses.
(b) Possible sample results for species A are shown in Figure 4.7(a) with the mean indicated by a circle on the boxplots. In the sample, is the mean greater for the resveratrol group? Can we necessarily conclude that resveratrol increases the metabolism rate for this species?
(c) Possible sample results for species B are shown in Figure 4.7(b) and the sample sizes are the same as for species A. For which of the two species, A or B, is the evidence stronger that resveratrol increases the metabolism rate for this species? Explain your reasoning.