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The several principal experimental matrices of the Auto/Oil Air Quality Improvement Research Program (AQIRP) were statistically designed as regards vehicle fleet size and fuel property combinations. The test results were analyzed using powerful standard statistical methods to extract the maximum amount of information from the data. The analysis included the use of appropriate data transformations and also graphical methods to display the results. The test fleets were sized to control the risk of failing to detect an important effect while providing assurance that unimportant, small effects have little chance to be found highly significant. To do this required estimation of the pertinent error term from other test programs which did not completely correspond to the type of testing contemplated in the AQIRP. These estimates turned out to be quite good. The compositional fuel matrices were blocked into two fuel groups.