Statistic Test Group Control Group
Mean Damage x¯1
= $ 1,094 x¯2
= $ 1,755
Sample Standard Deviation s1 = $ 706 s2 = $ 803
Repair Incidents n1 = 15 n2 = 13
Source: Unpublished study by Thomas W. Lauer and Floyd G. Willoughby.
(a) Construct a 99 percent confidence interval for the true difference of the means assuming equal variances.