Question 939765
an engineer sends 25 of the vehicles out on separate highway test routes. The sample mean fuel consumption
 rate is determined to be 7.8 ℓ/100 km with a standard deviation of 0.9ℓ/100 km.
 (a) Find a 95% confidence interval for the mean highway feul consumption rate for the vehicle.
sample mean = x-bar = 7.8
ME = z*s/sqrt(n) = 1.96*0.9/sqrt(25) = 0.353
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95% CI: 7.8-0.353 < u < 7.8+0.353
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 (b) Suppose that the engineer wants to be 95% confident that the estimated mean highway fuel consumption rate is within 0.1 &#8467;/100 km of the true mean highway consumption rate.How many vehicles should be sent out?
Since ME = z*s/sqrt(n), 
n = [z*s/E]^2 = [1.96*0.9/0.1]^2 = 312 when rounded up
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Cheers,
Stan H.
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