Crash testing is a highly expensive procedure to evaluate the ability of an automobile to withstand a serious accident. a simple random sample of 13 small cars were subjected to a head-on collision at 40 miles per hour. of them 8 were “totaled,” meaning that the cost of repairs is greater than the value of the car. another sample of 17 large cars were subjected to the same test, and 5 of them were totaled. let px represent the population proportion of small cars that are totaled and let py represent the population proportion of large cars that are totaled. find a 95% confidence interval for the difference px – py . round the answers to four decimal places.