As the automobile accident rate increases, insurers are forced to increase their
ID: 3358742 • Letter: A
Question
As the automobile accident rate increases, insurers are forced to increase their premium rates. Companies such as Allstate have recently been running a campaign they hope will result in fewer accidents by their policyholders. For each six-month period that a customer goes without an accident, Allstate will reduce the customer’s premium rate by a certain percentage. Companies like Allstate have reason to be concerned about driving habits, based on a survey conducted by Volvo of North America, in which 1,100 drivers were surveyed. Among those surveyed, 74% said that careless or aggressive driving was the biggest threat on the road. One-third of respondents said that cell phone usage by other drivers was the driving behavior that annoyed them the most.
Based on these data, assuming that the sample was a simple random sample, construct and interpret a 95% confidence interval estimate for the true proportion in the population of all drivers who are annoyed by cell phone users.
Explanation / Answer
given n=1100
p=0.74
95% Confidence interval for P is
where p=0.74 and z=1.96 and n=1100
Hence 95% CI for P is
(0.7141, 0.7659)
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