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This is an experiment that determines the effect of four different types of tips in a hardness tester on the observed hardness of a metal alloy. Four specimens of the alloy were obtained, and each tip was tested once on each specimen, producing the following data: Specimen Type of Tip 2 3 9.3 9.4 9.6 10.0 9.4 9.3 9.8 9.9 W N 9.2 9.4 9.5 9.7 9.7 9.6 10.0 10.2 (a) Is there any difference in hardness measurements between the tips? (b) Use Fisher's LSD method to investigate specific differences between the tips. (c) Analyze the residuals from this experiment. Please draw four plots: 1) normal probability plot of the residuals; 2) residuals versus Specimen; 3) residuals versus Type of Tip; 4) residuals versus fitted value