It currently takes users a mean of 15 minutes to install the most popular computer program made by RodeTech, a software design company. After changes have been made to the program, the company executives want to know if the new mean is now different from 15 minutes so that they can change their advertising accordingly. A simple random sample of 20 new customers are asked to time how long it takes for them to install the software. The sample mean is 14.1 minutes with a standard deviation of 1.9 minutes. Perform a hypothesis test at the 0.05 level of significance to see if the mean installation time has changed.

what is the ?

ho =

ha=

z statstic =

critical z value (write the value ofz orz/2)

Conclusion (write R for "reject H0", and F for "fail to reject H0") =