QUESTION 8

A manager is interested in improving productivity at a plant by changing the layout of the workstation. For each of 10 workers, she measures the time it takes to complete a task before the change and after the change. She calculates the following summary statistics for the sample difference: mean sample difference (between before and after) = 8.5 and sample standard deviation of the difference = 11.38. Assuming that the difference in time taken to finish the task is normally distributed, what is the critical value used to determine whether the mean difference (in task completion time) between before and after the change is not equal to zero at the 5% level of significance? Use our textbook statistical table to answer the question.

	a.	2.2622
	b.	1.96
	c.	2.1009
	d.	2.2281