Consider the seat belt usage data in Exercise 10-102. Find 95% CIs on the difference in the proportions of seat belt usage for drivers of foreign and domestic cars using both procedures described in this chapter. Compare the lengths of these two intervals and comment on any difference you may observe.

Exercise 10-102

In a random sample of 200 Phoenix residents who drive a domestic car, 165 reported wearing their seat belt regularly, and another sample of 250 Phoenix residents who drive a foreign car revealed 198 who regularly wore their seat belt.