Question: A two-factor experimental design was carried out, with factors A and B both categorical variables taking three values. Each treatment was applied four times and the following response values were obtained.
![552_Design.png](https://secure.tutorsglobe.com/CMSImages/552_Design.png)
Suppose we assume the normal regression model for these data with two categorical predictors.
(a) Produce a side-by-side boxplot for the data for each treatment.
(b) Produce a table of cell means.
(c) Produce a normal probability plot of the standardized residuals and a plot of the standardized residuals against each treatment combination (code the treatment combinations so there is a unique integer corresponding to each). Comment on the validity of the model.
(d) Construct the ANOVA table testing first for no interaction between A and B and, if necessary, an effect due to A and an effect due to Be Based on the results of part (d), construct the appropriate table of means.