Studies have shown that drivers who use cell phones while operating a motor passenger vehicle increase their risk of an accident. To quantify this risk, the New England Journal of Medicine (January 2, 2014) reported on the risk of a crash (or near crash) for both novice and expert drivers when using a cell phone. In a sample of 371 cases of novices using a cell phone while driving, 24 resulted in a crash (or near crash). In a sample of 1,467 cases of experts using a cell phone while driving, 67 resulted in a crash (or near crash).

a. Give a point estimate of p, the true crash risk (probability) for novice drivers who use a cell phone while driving.

b. Find a 95% confidence interval for p.

c. Give a practical interpretation of the interval, part b.

d. Repeat parts a–c for expert drivers.