Answer Happy

(Prob. 13-54, p. 571) An article in Lubrication Engineering (December 1990) described the results of an experiment designed to investigate the effects of carbon material properties on the progression of blisters on carbon face seals. The carbon face seals are used extensively in equipment such as air turbine starters. Five different carbon materials were tested, and the surface roughness was measured. The data are as follows: Carbon Material Type EC10 EC10A EC4 ECI Surface Roughness 0.50 0.55 0.55 0.36 0.31 0.07 0.25 0.18 0.56 0.20 0.20 0.28 0.12 0.10 0.16 (a) Does carbon material type have an effect on mean surface roughness? Use a = 0.05. (b) Find the residuals for this experiment. Does a normal probability plot of the residuals indicate any problem with the normality assumption? (c) Plot the residuals versus Yy. Comment on the plot. (d) Find a 95% confidence interval on the difference between mean surface roughness for the EC10 and the EC1 carbon grades.