Problem:

Crash testing is a highly expensive procedure to evaluate the ability of an automobile to withstand a serious accident. A simple random sample of 12 small cars were subjected to a head-on collision at40 miles per hour. Of them 8 were"totaled," meaning that the cost of repairs is greater than the value of the car. Another sample of15 large cars were subjected to the same test, and 5 of them were totaled.

Requirement:

Question: Find a 95% confidence interval for the difference in the proportions of small cars and large cars that are totaled.