Rework the decision problem in Example 7, supposing that only 3 of the 20 hard drives required repairs within the first year.

Data From Example 7

EXAMPLE 7 Comparing four detergents using an F test An experiment was designed to study the performance of 4 different detergents for cleaning fuel injectors. The following "cleanness" readings were obtained with spe- cially designed equipment for 12 tanks of gas distributed over 3 different models of engines: Engine Engine 2 Engine 3 Totals Detergent A 45 43 51 139 Detergent B 47 46 52 145 Detergent C 48 50 55 153 Detergent D 42 37 49 128 Totals 182 176 207 565 Looking at the detergents as treatments and the engines as blocks, obtain the appro- priate analysis of variance table and test at the 0.01 level of significance whether there are differences in the detergents or in the engines.