Swedish researchers investigated the relationship between chocolate consumption and stroke. The researchers gave a
questionnaire about eating habits to a randomly selected sample of
Swedish men. Based on the responses to the questionnaire, the men
were classified into two groups. Group A consisted of the 9, 250
men who ate the most chocolate per week, and group B consisted of
the 9, 250 men who ate the least chocolate per week. The
researchers tracked the men's health for ten years. During that
time, there were 458 cases of stroke among the men in group A and
543 cases of stroke among the men in group B. (a) Do the data provide convincing statistical evidence that
Swedish men who would be classified into group A have a lower
probability of stroke than Swedish men who would be classified
into group B?
(b) A report in a newspaper concluded that Swedish men can
reduce their probability of stroke by eating more chocolate. Based
on the description of the investigation, was the conclusion
appropriate?