2) In 1990, about 40% of U.S. adult population had never smoked cigarettes. A national health
survey of 1200 U.S. adults (presumably selected randomly) during 2010 revealed that 540 had never
a) Construct 95% confidence interval for the true proportion of U.S. adults in 2010 that have never smoked
cigarettes and interpret this interval.
b) Suppose you wished to test whether there has been a change since 1990 in the proportion of U.S. adults
that have never smoked cigarettes. Use 0.01 significance level to test this belief.
(ii) Value of the test statistic:
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