8. Now you will obtain some diagnostic plots to verify the model assumptions for the model found in question 7. (a) Obtain a plot of residuals versus the fitted values for the model found in question 7. Paste the plot into your report. Is there evidence that the variance of the residuals changes with increasing fitted values or that there are any outliers? Explain briey. (b) Obtain a normal probability plot of standardized residuals for the model found in question 7. Paste the plot into your report. Is there any evidence that the assumption of normality is violated? Comment