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# Confidence Interval-difference between means (small sample)

The university data center has two main computers. The center wants to examine whether computer 1 is receiving tasks that require processing times comparable to those of computer 2. A random sample of 10 processing times from computer 1 showed a mean of 69 seconds with a standard deviation of 15 seconds, while a random sample of 11 processing times from computer 2 (chosen independently of those for computer 1) showed a mean of 67 seconds with a standard deviation of 17 seconds. Assume that the populations of processing times are normally distributed for each of the two computers and that the variances are equal. Construct a 95%confidence interval for the difference M1-M2 between the mean processing time of computer 1,M1 , and the mean processing time of computer 2, M2. Then complete the table below.

1. What is the lower limit of 95% confidence interval?

2. What is the upper limit of 95% confidence interval?