10.74 BMI then and now The Centers for Disease Control

(www.cdc.gov) periodically administers large randomized surveys to track health of Americans. In a survey of 4431 adults in 2003/2004, 66% were overweight (body mass index BMI Ú 25). In the most recently available survey of 5181 adults in 2011/2012, 69% were overweight.

a. Estimate the change in the population proportion who are overweight and interpret.

b. The standard error for estimating this difference equals 0.0096. What is the main factor that causes se to be so small?

c. The 95% confidence interval comparing the population proportions in 2011/2012 to the one in 2003/2004 is

(0.011, 0.049). Interpret, taking into account whether 0 is in this interval.