(Solved): (b) Repeat part (a), using the assumption of unequal varlances with Welch's formula for ...

(b) Repeat part (a), using the assumption of unequal varlances with Welch's formula for d.f. (Round the calculation for Welch's df to the nearest integer. Round your final answers to 3 decimal places. Negative values should be indicated by a minus sign.) A special bumper was installed on selected vehicles in a large fleet. The dollar cost of body repairs was recorded for all vehicles that were involved in accidents over a 1-year period. Those with the special bumper are the test group and the other vehicles are the control group, shown below. Each "repair incident" is defined as an invoice (which might include more than one separate type of damage). Source: Unpublished study by Thomas W. Lauer and Floyd G. Willouynuy. (a) Construct a 99 percent confidence interval for the true difference of the means assuming equal variances. (Round your final answers to 3 decimal places. Negative values should be indicated by a minus sign.) Yes No (d) Construct separate $$99\%$$ confidence intervals for each mean. (Round your intermediate tcrit value to 3 decimal places. Round your final answers to 2 decimal places.)