A large aircraft parts manufacturing company in LA has over 1900 employees. The

Question

A large aircraft parts manufacturing company in LA has over 1900 employees. The president of the company wants to estimate the average engineering experience (in years) of her employer's preliminary random sample of 70 employees yields a sample standard deviation of s = 1.7 years. The employer wants to be 99% confident that the sample mean X(bar) does not differ from the population mean by more than a year. How large a sample should be used?

A) 43                  B) 5,799                 C) 250              D) 25                 E) 77

Explanation / Answer

n = (zc *Standard deviation)^2 / Margin of Error^2

zc we find from normal table at 1% level of significance as 2.58

n = (2.58*1.7)^2 / 1^2

   = 19.17

~ 20

Here the 20 is not given in the option. We choose the closest one and it is 25

Answer:

Option D) 25

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