Do positive emotions reduce susceptibility to colds? Healthy volunteers were divided into two groups based on their emotional pro les and each group was exposed to rhinovirus (the common cold). Of those who reported mostly positive emotions, 14 of 50 developed cold symptoms, compared with 23 of 56 who reported mostly negative emotions.
(a) Find the 95 percent confidence interval for the difference in proportions. What does it suggest?
(b) Is the criterion for normality met?