Determine Sample Size for a Confidence Interval
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Until this year the mean braking distance of a Yamashita motorcycle moving at 60 miles per hour was 160 feet. Yamashita engineers have developed what they consider a better braking system. They test the new braking system on a random sample of 20 motorcycles and determine the sample mean to be 145 feet, with a sample standard deviation of 25 feet.
How many motorcycles should be tested if Yamashita wants to be 95% confident of being within 5 feet of the population mean braking distance?
t value =
Express your answer to three decimal places.
Sample size =
Use MegaStat to find your t-value, and then use a scientific calculator for your final computations.
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Solution Summary
The Solution provides the required sample size.
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