Question

The mean length of time required to perform a certain assembly line task at Joe's Manufacturing has been established to be 15.5 minutes, with a standard deviation of 3 minutes. A random sample of 9 employees is taught a new method. After a training period, the average time these 9 employees take to preform the same task is 13.5 minutes. The plant manager would like to be at least 97.5% sure before switching any more employees to the new, perhaps faster method and consults you for advice. Do these results provide sufficient evidence to indicate that he new method is faster than the old? Use the critical value approach to develop and test the appropriate hupotheses concerning this situation. What would you advise the manager under these circumstances?

Answer 1

H0: Null Hypothesis: 15.5

HA: Alternative Hypothesis: 15.5

SE = /

= 3/ = 3/3 =1

Test statistic is:

t = (13.5 - 15.5)/1 = - 2

= 0.025

ndf = n - 1 = 9 - 1 = 8

One Tail Test - Left Side

By Technology, critical value of t = - 2.3060

Since the calculated value of t = - 2 is greater than critical value of t = - 2.3060, the difference is not significant. Fail to reject null hypothesis.

Conclusion:

The data do not support the claim that the mean length of time required has reduced after training in new method.We advice the manager under te circumstances that the new training method is not effective.