Question

At a large company, the Director of Research found that the average work time lost by employees due to accidents was 94 hours per year. She used a random sample of 20 employees. The standard deviation of the sample was 5.9 hours. Estimate the population mean for the number of hours lost due to accidents for the company, using a 95% confidence interval. Assume the variable is normally distributed. Round intermediate answers to at least three decimal places. Round your final answers to the nearest whole number.

Answer 1

Given :

We need to find 95% confidence interval ,

As population standard deviation is unknown ( not given ) , we use t-interval .

c = 0.95

Degrees of freedom = n-1 = 20-1 =19

df = 19

Using excel function , =TINV( , df)

=TINV( 0.05 , 19 )

=2.093

Now plug the values in the formula ,

Rounding to nearest whole number

The 95% confidence interval for the population mean for the number of hours lost due to accidents for the company is (91 , 97)