SOLUTION: Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 years. Assum

Question 1105005: Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 years. Assume the sample standard deviation is 4.8 years. Your preliminary sample will be at least 30.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
start with n=30, t(0.975,df=29) is 2.042
the interval 0.5=2.042*s/sqrt (n)
sqrt(n)=2.042*4.8/0.5=19.60
square both sides an n=384.3, round to 385.
interval for this sample size has a t about 1.96, and since 1.96 will not change significantly with a slightly smaller sample, solve by 1.96*4.8/sqrt(n)=0.5. That is 354.04 or 355.

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