A customer service representative was interested in comparing the average time (in minutes) customers are placed on hold when calling Southern California Edison and Southern California Gas companies....

A customer service representative was interested in comparing the average time (in minutes) customers are placed on hold when calling Southern California Edison and Southern California Gas companies. The representative obtained two independent random samples and calculated the following summary information: So Cal Edison

Assume the distributions of time a customer is on hold are approximately normal.

Using the null and alternate hypothesis:
H0:mu1-mu2=0 vs. Ha:mu1-mu2 not equal 0

Calculate the value of the test statistic.