A HR manager conducted a review of overtime worked by employees. Her sample size was 60 employees and there was a mean of 90 hours worked overtime per month. Her confidence interval was 95%. What would be the upper boundary confidence interval for this study?
A) 91.86 hours
B) 88.14 hours
C) 90 hours
D) 9.5 hours

Question

Quizplus · Accepted Answer

Since we are looking for the upper boundary of the confidence interval, we need to use the upper limit of the interval formula. Using a 95% confidence interval, the formula is: 
Upper limit = mean + (Z-score x standard error)
The Z-score for a 95% confidence interval is 1.96. To calculate the standard error, we need to divide the standard deviation by the square root of the sample size. Assuming a standard deviation of 10 hours, the standard error would be:
Standard error = 10 / sqrt(60) = 1.29
Plugging in these values, we get:
Upper limit = 90 + (1.96 x 1.29) = 91.86 hours
Therefore, the correct choice is A.

A HR Manager Conducted a Review of Overtime Worked by Employees