Astudy1 examines chocolate’s effects on blood vessel function in healthy people. in the randomized, double-blind, placebo-controlled study, 11 people received 46 grams (1.6 ounces) of dark chocolate (which is naturally flavonoid-rich) every day for two weeks, while a control group of 10 people received a placebo consisting of dark chocolate with low flavonoid content. participants had their vascular health measured (by means of flow-mediated dilation) before and after the two-week study. the increase over the two-week period was measured, with larger numbers indicating greater vascular health. for the group getting the good dark chocolate, the mean increase was 1.3 with a standard deviation of 2.32, while the control group had a mean change of -0.96 with a standard deviation of 1.58. 1engler, m., et. al., ‘‘flavonoid-rich dark chocolate improves endothelial function and increases plasma epicatechin concentrations in healthy adults," journal of the american college of nutrition, 2004 jun; 23(3): 197-204. (a) find a 95% confidence interval for the difference in means between the two groups μc-μn, where μc represents the mean increase in flow-mediated dilation for people eating dark chocolate every day and μnrepresents the mean increase in flow-mediated dilation for people eating a dark chocolate substitute each day. you may assume that neither sample shows significant departures from normality.