CR design - Ex. 8.29 (p. 444)

a) stack data
Data > Stack > Stack Columns...
Stack the following columns: Group-I Group-II Group-III Group-IV
Choose "Column of current worksheet:"  C5
Store subscripts in: C6
Click OK
You may rename C5 as discoloration and C6 as group (or treatment)

b) Boxplots by trt
Stat > Basic Statistics > Display Descriptive Statistics...
Variables: discoloration
Check "By variable:" group
Click on Graphs...
Check Boxplot of data
Click OK twice

c) ANOVA
Stat > ANOVA > One-way...
Response: discoloration
Factor: group
You can check "Store residuals" and "Store fits" to have the residuals 
and fitted values stored in the worksheet
You can also click the "Graphs..." button to have the residual plots (normal
probability plot (NPP) of residuals, scatter plot of residuals vs. fitted values, etc.)
 
d) checking assumptions
The main assumptions to check are the normality and equal variance assumptions.
Use the NPP of residuals to check the normality assumption.
Use the boxplots by trt and the standard deviations by trt to check the 
equal variance assumption. If you want a formal test, use
Stat > ANOVA > Test for Equal Variances...