Chapter 6, Problem 6.131ACI

Cell phone use by drivers. Studies have shown that drivers who use cell phones while operating a motor passenger vehicle increase their risk of an accident. Nevertheless, drivers continue to make cell phone calls while driving. A June 2011 Harris Poll of 2,163 adults found that 60% (1.298 adults) use cell phones while driving.

1. a. Give a point estimate of p, the true driver cell phone use rate (i.e., the proportion of all drivers who are using a cell phone while operating a motor passenger vehicle).
2. b. Find a 95% confidence interval for p.
3. c. Give a practical interpretation of the interval, part b.
4. d. Determine the margin of error in the interval if the number of adults in the survey is doubled.