Question

The days of training a new employee needs are normally distributed with a population standard deviation of 3 days and an unknown population mean. If a random sample of 23 new employees is taken and results in a sample mean of 18 days, use Excel to find a 90% confidence interval for the population mean.

Round the final answer to two decimal places.

Answer 1

Solution :

Using Excel ,

90%	confidence level
18	mean
3	std. dev.
23	n
1.717	t (df = 22)
1.074	half-width
19.074	upper confidence limit
16.926	lower confidence limit

A 90% confidence interval for the population mean is : (16.93 , 19.07)