Question

A random sample of 1500 residential telephones in Phoenix found that 385 of the numbers were unlisted. A random sample in the same year of 1200 telephones in Scottsdale found that 311 were unlisted.

Round your answers to four decimal places (e.g. 98.7654).

(a) Calculate a 95% two-sided confidence interval on the difference in the proportions of unlisted numbers between the two cities.
Enter your answer; 95% confidence interval, lower bound ≤p1-p2≤ Enter your answer; 95% confidence interval, upper bound

(b) Is there a significant difference between the two proportions at α = 0.05? Choose your answer in accordance to the item b) of the question statement                                                          No.Yes.

(c) Calculate a 90% two-sided confidence interval on the difference in the proportions of unlisted numbers between the two cities.
Enter your answer; 90% confidence interval, lower bound ≤p1-p2≤ Enter your answer; 90% confidence interval, upper bound

Answer 1