The National Health Interview Survey conducted of 27 603 adults by
The National Health Interview Survey conducted of 27,603 adults by the U.S. National Center for Health Statistics in 2009 indicated that 20.6% of adults were current smokers. A similar study conducted in 1991 of 42,000 adults indicated that 25.6% were current smokers.
a. Find and interpret a point estimate of the difference between the proportion of current smokers in 1991 and the proportion of current smokers in 2009.
b. A 99% confidence interval for the true difference is (0.042, 0.058). Interpret.
c. What assumptions must you make for the interval in part b to be valid?
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