119 Cell phone use by drivers. The U.S. Department of Transportation reported the results of the National Occupant Protection Use Survey . One focus of the survey was to determine the level of cell phone use by drivers while they are in the act of driving a motor passenger vehicle. Data collected by observers at randomly selected intersections across the country revealed that in a sample of 1,165 drivers, 35 were using their cell phone.

a. Give a point estimate of p , the true driver cell phone use rate (i.e., the true proportion of drivers who are using a cell phone while driving).

b. Compute a 95% confidence interval for p .

c. Give a practical interpretation of the interval you found in part b .

d. How many drivers need to be sampled to estimate the true cell phone use rate to within .005 with 95%

confidence?