Until this year the mean braking distance of a Matsumura moped moving at 35 mile

Question

Until this year the mean braking distance of a Matsumura moped moving at 35 miles per hour was 50 feet. Matsumura engineers have developed what they consider a better braking system. They test the new braking system on a random sample of 25 mopeds and determine the sample mean to be 45 feet, with a sample standard deviation of 10 feet.

How many mopeds should be tested if Matsumura wants to be 95% confident of being within 3 feet of the population mean braking distance?

t-value= ( do not round the t-value)

Sample size= (enter the smallest whole number that will yield the desired error)

Explanation / Answer

Given s=10, E=3 a=0.05, t(0.025, df=n-1=24)=2.06 (check student t table) So n=(t*s/E)^2 = (2.06*10/3)^2 =47.15111 Take n=48

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