The Pew Forum on Religion and Public Life reported on Dec. 9, 2009, that in a survey of 2003 American adults, 25% said they believed in astrology. a. Calculate and interpret a confidence interval at the 99% confidence level for the proportion of all adult Americans who believe in astrology. b. W

The confidence interval at the 99% confidence level for the proportion of all adult Americans who believe in astrology is (0.2251, 0.2749). This means that we are 99% sure that the true proportion of all adult Americans who believe in astrology is in this interval.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of , we have the following confidence interval of proportions.

In which

z is the zscore that has a pvalue of .

For this problem, we have that:

99% confidence level

So , z is the value of Z that has a pvalue of , so .

The lower limit of this interval is:

The upper limit of this interval is:

The confidence interval at the 99% confidence level for the proportion of all adult Americans who believe in astrology is (0.2251, 0.2749). This means that we are 99% sure that the true proportion of all adult Americans who believe in astrology is in this interval.