Question

Work Time Lost due to Accidents At a large company, the Director of Research found that the average work time lost by employees due to accidents was hours per year. She used a random sample of employees. The standard deviation of the sample was hours. Estimate the population mean for the number of hours lost due to accidents for the company, using a 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

(95.215 ; 100.785)

(95 ; 101) (nearest whole number)

Explanation:

To obtain the confidence interval :

Mean ± margin of error

Mean = 98 hours

Margin of Error = Tcritical * (s/√n)

samole standard deviation, s = 5.6 hours

df = n - 1 = 18 - 1 = 17

Tcritical at (0.05, df = 17) = 2.110

Hence ;

Margin of Error = 2.110 * (5.6/√18) = 2.785

Confidence interval :

98 ± 2.785

Lower boundary = 98 - 2.785 = 95.215

Upper boundary = 98 + 2.785 = 100.785

(95.215 ; 100.785)