In 1965, about 44% of the U.S. adult population had never smoked cigarettes. A national health survey of 1205 U.S. adults (presumably selected randomly) during 2006 revealed that 615 had never smoked cigarettes.

Reference: Ref 18-5

A 96% confidence interval for the proportion of U.S. adults in 2006 that have never smoked is

a.0.461 to 0.560.

b.0.481 to 0.540.

c.0.470 to 0.551.

d.0.487 to 0.534