A telephone poll reported in Time magazine (6 February 1995, p. 24) asked 359 adult Americans the question: “Do you think Congress should maintain or repeal last year’s ban on several types of assault weapons?” Seventy-five percent responded “maintain.”
a. Compute the standard error that accompanies the sample proportion of .75.
b. Time reported that the “sampling error is ± 4.5%.” Verify that 4.5% is approximately what would be added and subtracted to the sample percentage to create a 95% confidence interval. (It is equivalent to a margin of error of .045 for a confidence interval for the population proportion.)
c. Use the information reported by Time to create a 95% confidence interval for the population proportion. Interpret the interval in words that would be understood by some­one with no training in statistics. Be sure to specify the population to which it applies.
d. The ban was in place for 10 years, but repealed in 2004. In 2013, after some high-profile cases of gun violence, the topic was in the news again. In March, 2013, a Quinnipiac Univer­sity poll asked 1711 adults: “Do you support or oppose a nationwide ban on the sale of assault weapons?” Fifty-nine percent said “Support.”
(www.pollingreport.com/guns.htm). Find a 95% confidence interval for the population proportion that supported this ban in March, 2013.
e. Compare the confidence intervals found in parts (c) and (d). Write a few sentences explaining whether support for banning these weapons seemed to increase or decrease between 1994 and 2013.