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Q.11

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The Practice of Statistics for AP
Found in: Page 482
The Practice of Statistics for AP

The Practice of Statistics for AP

Book edition 4th
Author(s) David Moore,Daren Starnes,Dan Yates
Pages 809 pages
ISBN 9781319113339

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Short Answer

Prayer in school A New York Times/CBS News Poll asked the question, “Do you favor an amendment to the Constitution that would permit organized prayer in public schools?” Sixty-six percent of the sample answered “Yes.” The article describing the poll says that it “is based on telephone interviews conducted from Sept. 13 to Sept. 18 with 1664 adults around the United States, excluding Alaska and Hawaii. . . . The telephone numbers were formed by random digits, thus permitting access to both listed and unlisted residential numbers.” The article gives the margin of error for a 95% confidence level as 3 percentage points.

(a) Explain what the margin of error means to someone who knows little statistics.

(b) State and interpret the 95% confidence interval.

(c) Interpret the confidence level.

a). On average the sample proportion will be within 3% of the true proportion in 95% of all samples.

b). We are localid="1649754733996" 95% confident that the true population proportion is between localid="1649754744695" 0.63 and localid="1649754756510" 0.69.

c). On average, in localid="1649754767371" 95% of all samples the corresponding confidence interval will contain the true population proportion localid="1649754793252" p.

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Step by Step Solution

Part (a) Step 1: Given Information 

The article gives the margin of error for a 95% confidence level as 3 percentage points.

Part (a) Step 2: Explanation 

The margin of error is the amount of error that is made, on average, in estimating the population proportion p by the sample proportion p^.

Thus on average the sample proportion will be within 3% of the true proportion in 95% of all samples.

Part (b) Step 1: Given Information 

The article gives the margin of error for a 95%.

p^=66%=0.66

E=3%=0.03

Part (b) Step 2: Explanation 

The boundaries of the confidence interval is the sample proportion increased/decreased by the margin of error:

0.63=0.66-0.03=p^-E<p<p^+E=0.66+0.03=0.69

We are 95% confident that the true population proportion is between 0.63 and 0.69.

Part (c) Step 1: Given Information 

The article gives the margin of error for a 95% confidence level.

Part (c) Step 2: Explanation 

The confidence level is 95%.

This means: On average, in 95% of all samples the corresponding confidence interval will contain the true population proportion p.

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