21.1. The 95% confidence interval for the proportion of all adult Americans who believe gambling is morally wrong is

Interpret this result as follows: we got this interval by using a recipe that catches the true unknown population proportion 95% of the time. The shorthand is, we are 95% confident that the true proportion of adult Americans who believe gambling is morally wrong lies between 28.2% and 33.8%.

21.2. The 99% confidence interval for the proportion of all adult Americans who believe gambling is morally wrong is

Interpret this result as follows: we got this interval by using a recipe that catches the true unknown population proportion 99% of the time. The shorthand is, we are 99% confident that the true proportion of adult Americans who believe gambling is morally wrong lies between 27.4% and 34.6%.

21.3. The 95% confidence interval for μ uses the critical value z* = 1.96 from Table 21.1. The interval is

= 126.1 ± 1.96(1.79)

= 126.1 ± 3.5

We are 95% confident that the mean blood pressure for all executives in the company between the ages of 35 and 44 lies between 122.6 and 129.6.