An experiment was conducted on the growth rates of tree seedlings by selecting seeds from 4 varieties of trees (denoted Victoria1, Victoria2, Clinton, and Branch). Four regional blocks were selected where within each block, 1 ha plots were planted with seedlings from each variety. Then within each 1 ha plot, four 100 m2 sub-plots were selected, and one of 4 different sprays were sprayed on the seedlings. These four treatments were denoted as (Check, Ceresan, Panogen, and Agrox). The data can be found found at trees.csv
- What is the experimental design?
- Create an interaction plot for the variety.
- Create an ANOVA table and perform relevant tests.
- Is interaction significant? Do your results agree with part (b)?
- Do you think it is a good idea to remove a variety from the data and analyze seperately? Explain.
If yes.
- How would you analyze the spray for that one variety, i.e. what design would you use? Hint: It might be helpful to visualize the data in wide format.
- Analyze the remainder of the data (with that one variety removed). Plot interaction plots, determine which effects are significant and perform pairwise Tukey 95% comparisons.
- If no, which effects are significant? Perform pairwise Tukey 95% comparisons