hypothesis testing PLEASE HELP

#1
I don't really know how to tell what test to use with this questio. I think that it is ttest or z. could you please help. I have done so much reading about hypothesis testing that I am confused. This is a short course and online. There has been no real teaching of the subject, we are supposed to get it all from the readings.:confused: :confused:

The new director of special programs in XYZ Corporation felt the customers were waiting too long to receive and complete forms needed to enroll in special programs. After collecting some data, Ms. Jones determined the mean wait time was 28 minutes. She felt this time period was excessive and she instituted new procedures to streamline the process. One month later, a sample of 127 customers was selected. The mean wait time recorded was 26.9 minutes and the standard deviation of the sampling was 8 minutes. Using the .02 level of significance, conduct a five-step hypothesis testing procedure to determine if the new processes significantly reduced the wait time.
 

KimR

New Member
#2
t test or z test

I would say, with the information given, you need to consider the difference between the z and t tests. The z test has an assumption that the population parameters are known, but the t test does not. Since you are looking at 2 sample groups, I would say the t test is the better way to go.