11. The National Health Interview Survey conducted of 42.000 adults by the U.S. National Center for Health Statistics in 1991 indicated that 25.6% of adults were current smokers A similar study conducted in 1965 indicated that 42.4% were cunent smokers

a) Construct a 95% confidence interval for the difference between the proportion of cur- rent sinokers in 1965 and the proportion of current smokers in 1991 (Assume that the sample size was the same in 1965.) Interpret.

b) Using the standard error from the confidence interval. test that there was no change in the proportion of current smokers Report the test statistic and P-value, and interpret.

c) What statisucal factors cause the test statistic in

(b) to be so large"