# Computing Confidence Intervals for Population Proportions

Question 3

Calculate a 95% Confidence Interval (CI) for the true population proportion with successful treatment. Hint: The SE of p is the square root of (pq)/n. (40 pts)

Upper limit CI = _____ (20 pts)

Lower Limit CI = _____ (20 pts)

Question 4

Which of the following is true with regard to the confidence interval computed in Question 3 above: (25 pts)

a. 95 times out of 100 one would expect a the sample of 399 taken from the same population to have a proportion of successfully treated patients to be between the upper and lower limits of the confidence interval computed in Question 2.

b. 95 times out of 100 one would expect a the sample of 399 taken from the same population to have a proportion of successfully treated patients to be outside the upper and lower limits of the confidence interval computed in Question 2.

c. 5 times out of 100 one would expect a the sample of 399 taken from the same population to have a proportion of successfully treated patients to be outside the upper and lower limits of the confidence interval computed in Question 2.

d. a and c.

(See attachment for data)

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Question 3: since estimated p is 275/399=0.689, standard error of estimated p is ...

#### Solution Summary

The solution gives detailed steps on computing confidence intervals for population proportions . All formula and calculations are shown and explained. An interpretation is also given.