Confidence Interval

Hi all,

I was hoping someone could clarify a question I am stuck on.

The 95% confidence interval of the sample mean of employee age for a major corporation is 19 years to 44 years based on a a z-statistic. The population of employees is more than 5,000 and the sample size of this test is 100. Assuming the population is normally distributed, the standard error of mean employee age is closest to:

A. 1.96

B. 2.58

C. 6.38

The answers is C, 6.38 - but I have trouble understanding why.

Any insights would be hugely appreciated.

Jim

First find the range of interval and divide by two: 44 - 19 = 25, 25/2 = 12.5

Divide 12.5 by 1.96 (standard deviations of 95% CI) = 6.377 or 6.38

Thanks very much for responding Dass

I see what is happened with the Math, but I am unsure what the logic is in dividing the range by 2 then dividing that value by 1.96.

If possible would you be able to explain the why?

Thanks so much in advance

Ahh I have got it now - Thanks Dass :slight_smile: