Standard error

The 95% confidence interval of the sample mean of the employee age for a major corporation is 19 to 44 years based on a z-statistics. The population of employees is more than 5000 employees 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 answer should be C.

Upper Confidence Intervall: X Mean + za/2 * standard error

Given: X Mean =(19+44)/2 = 31.5 (mean lies always in the middle of the confidence intervall) za/2 = 1,96 (corresponding to the 95% confidence intervall) Upper confidence intervall: 44

Put the given data in the formula above and solve for the standard error. Result is 6.38.

C should be correct.

Regards, Oscar

To calculate standard error is it not: Standard Deviation/ Sqr Rt Sample.

In this case how did you get the standard deviation to work it out?

We didn’t get it, we just did mathematical manoeuvring :slight_smile: