Question: The following values of a response Y were obtained for three settings of a categorical predictor A

Suppose we assume the normal regression model for these data with one categorical predictor.

(a) Produce a side-by-side boxplot for the data.

(b) Plot the standardized residuals against A (if you are using a computer for your calculations, also produce a normal probability plot of the standardized residuals) Does this give you grounds for concern that the model assumptions are incorrect?

(c) If concerns arise about the validity of the model, can you "fix" the problem?

(d) If you have been able to fix any problems encountered with the model, carry out a one-way ANOVA to test for any differences among the conditional means of Y given A(e) If warranted, construct 0.95-confidence intervals for the differences between the means and summarize your findings.