SOLUTION: An automobile road service company wishes to estimate the proportions of the different emergency road services (ERS) requests. Upon examining a sample of 3000 ERS calls it finds th

Question 1031952: An automobile road service company wishes to estimate the proportions of the different emergency road services (ERS) requests. Upon examining a sample of 3000 ERS calls it finds that 1450 calls related to starting problems, 850 calls involved serious mechanical failures requiring towing, 500 calls involved flat tires or lockouts, and 200 calls were for other reasons.
a) Estimate the true proportion of ERS calls that involved serious mechanical failures requiring towing. (Round your answer to two decimal places).
b) Construct the 99% confidence interval for the true proportion of ERS calls that involved serious mechanical failures requiring towing. (Round your answers to two decimal places).
c) Interpret the results of part b.

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
The point estimate is 850/3000=0.28
The 99%CI is
2.576+/- sqrt(.28)(.72)/sqrt(3000)=0.021
to two decimal places, the 99%CI is (0.26,0.30)
We don't know the true proportion of calls that will require towing, but we are highly confident the number resides in the range (0.26,0.30).
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