Question

An auto insurance company wants to know the proportion of drivers who always buckle their seat belts when driving. They randomly survey 400 drivers and find that 320 always buckle up. What is the 99% confidence interval for the population proportion of drivers who always buckle their seat belt? Round to 3 decimal places.

Answer 1

Answer Date: 11/11/2019 The 99% confidence interval for the population proportion of drivers who always buckle their seat belt is, First, compute the proportion, the Z-critical value then find confidence interval. The proportion is, 320 400 = 0.800 The Z-critical value is, From the standard normal table, the z-critical value at 99% confidence is 2.576.

(1-P) 99%C.I. = pzcx = 0.80 +2.576 x 0.80(1-0.80) 400 = 0.748 to 0.852 The 99% confidence interval for the population proportion of drivers who always buckle their seat belt is 0.748 to 0.852 .