
167More on Inferential Statistics
(continued)
14 C Var4 66.1
15 C Var5 65.3
16 D Var1 69.5
17 D Var2 69.7
18 D Var3 68.9
19 D Var4 69.3
20 D Var5 68.3
> attach(yield.tv)
To simplify repeated use in the next few statements, we attach this data frame. For visual inspection,
graph boxplots for factors. We do not need to declare the data set in the boxplot function because
we have attached yield.tv
> par(mfrow=c(2,1) )
> boxplot(yield ~ var, ylab=“Yield”, xlab=“Var”)
> boxplot(yield ~ treat, ylab=“Yield”, xlab=“Treat”)
We obtain results as in Figure 5.5 already discussed. Then graph an interaction plot to check for
possible factor interactions
> interaction.plot(treat, ...