Ever since President John F. Kennedy was assassinated in 1963, there has been speculation about whether there was a single assassin or more than one. Periodically, public opinion polls ask this question: “Turning now to the assassination of John F. Kennedy in 1963—Do you think that one man was responsible for the assassination of President Kennedy, or do you think that others were involved in a conspiracy?”
(www.pollingreport.com/news3.htm#Kennedy). www.pollingreport.com/news3.htm#Kennedy). In a poll of 533 adults in the United States in 2003, 400 (i.e., 75%) of them responded “Others involved.” In a poll of 1004 U.S. adults in 2013, 592 (i.e., 59%) of them responded “Others involved.” An approximate 95% confidence interval for the difference in population percentages who felt that way in 2003 versus 2013 is 16% ± 5%, with the higher percentage in 2003.
a. Compute the endpoints of the interval.
b. Write a sentence or two interpreting the interval in words that would be understood by someone with no training in statistics.
c. Does the interval indicate that opinion on this issue changed between 2003 and 2013 for the population of U.S. adults? Explain.