Groups Comparison With ANOVA: Exercises (Part 2)

On this 2nd part of groups comparison exercise, we will focus on nested ANOVA application in R, particularly the application on ecology. This is the last part of groups comparison exercise.Previous exercise can be found here
Answers to the exercises are available here. If you obtained a different (correct) answer than those listed on the solutions page, please feel free to post your answer as a comment on that page.
To recall our previous exercise, below is the flowchart of group comparison process.

Download dataset required : here

Exercise 1
Load required package; car,ggplot2,dplyr,lattice, alr4 and check if the dataset is in balance using table and or replication function

Exercise 2
Determine the Null hypothesis and create some data visualizations including histogram, boxplot and coplot

Exercise 3
Chcek for normality and homogeneity of variance

Exercise 4
Check for interaction between explanatory variables using interaction plot and or xyplot

Exercise 5
Select the appropriate model ANOVA based on the interaction (nested model)

Exercise 6
Select nested model ANOVA based on Food effect

Exercise 7
Select nested model ANOVA based on Pen Effect

Exercise 8
Comparing those two nested models and generate some conclusions