Williams Software purchases its PCs from two different manufacturers. Most of the bugs are worked out a few weeks after a new machine is installed, but only after several phone calls are placed to the manufacturer’s technical support staff. Frank Williams, the company’s PC buyer, has asked the programmers to keep a log of the number of minutes spent on the phone with each company for three weeks after installation. Results stemming from last year’s activity with new machines are shown in the table below:
Company A
Installed computers – 18
Minutes per machine – 57.3
Standard deviation – 6.1
Company B
Installed computers – 16
Minutes per machine – 69.7
Standard deviation – 9.2
a. Calculate the pooled variance for the data.
b. Set up the hypotheses to test if the time spent with the technical staff of the two manufacturers is the same. Use a small population test with equal variances and level of significance 0.05.
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