Inferences of Mu1 Mu2 with sigma1 sigma2 An article in Nat

Inferences of Mu_1 - Mu_2 with sigma_1 = sigma_2. An article in Nature (2003, Vol. 48, p. 1013) described an experiment in which subjects consumed different types of chocolate to determine the effect of eating chocolate on a measure of cardiovascular health. We will consider the results for only dark chocolate and milk chocolate. In the experiment, 12 subjects consumed 100 grams of dark chocolate and 200 grams of milk chocolate, one type of chocolate per day, and after one hour, the total antioxidant capacity of their blood plasma was measures in an assay. The subjects consisted of seven women and five men with an average age range of 32.2 plus or minus 1 years, an average weight of 65.8 plus or minus 3.1 kg, and average body mass index of 21.9 plus or minus 0.4 kh/m^2. Data similar to that reported in the article follows. Dark Chocolate: 118.8, 122.6, 115.6, 113.6, 119.5, 115.9, 115.8, 115.1, 116.9, 115.4, 115.6, 107.9. Milk Chocolate: 102.1, 105.8, 99.6, 102.7, 98.8, 100.9, 102.8, 98.7, 94.7, 97.8, 99.7, 98.6. Let Mu_1 be the mean blood plasma antioxidant capacity resulting from eating dark chocolate and Mu_2 be the mean blood plasma antioxidant capacity resulting from eating milk chocolate. According to the box plots in Figure 1 or sample standard deviations, do you believe that the population standard deviations are equal? Why? Calculate a two-sided 95% on the mean difference Mu_1 - Mu_2 of blood plasma antioxidant capacities. Is there evidence to support the claim that consuming dark chocolate produces a higher mean level of total blood plasma antioxidant capacity that consuming milk chocolate? Use significant level alpha = 0.05. What is your conclusion? Do normal qq plots of blood plasma antioxidant capacity in Figure 2 indicate any violations of the assumptions for the tests and confidence interval that your performed?

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