Chapter 9.1, Problem 9.3E

To determine

To explain the meaning of 95% confidence.

Explanation of Solution

Given:

A 2007-2008 survey of teens conducted by the Partnership for a Drug-Free America found that 33% of 6511 U.S. teenagers surveyed reported use of marijuana. The report states, "With 95% confidence, we can say that between 31.4% and 34.6% of all-American teenagers have used marijuana."

In the given study, population proportion of use of marijuana is 33%. The 95% confidence interval for population proportion is, (31.4%, 34.6%). That is, researcher is 95% confident that the population proportion of use of marijuana will fall within (31.4%, 34.6%) this interval.