597 / 762
Chapter 13: Confidence Intervals – Small Samples
597
difference between the two population means will be between -2.2305 and
10.2305.
Observe that the computations are quite lengthy. However, we can use the
Small Sample Confidence Interval for the Difference between Two
Independent Means
workbook to help with these computations
. Figure
13-9
shows the workbook output for the problem.
Figure 13-9:
Workbook Output with the Confidence
Interval for
Example 13-5
Thus from the output, the 99% confidence interval estimate for the
difference of the means for the two populations (average for the foreign car
mpg – average for the domestic car mpg) is (-2.2309, 10.2309). That is, we
are 99% confident that the difference between the two population means will
be between -2.2309 and 10.2309.