The Linthurst data used in Chapters 5 and 7 came from nine sites classified according to location (LOC ) and type of vegetation (TYPE). (The data are given in Table 5.1.) Do the analysis of variance...

The Linthurst data used in Chapters 5 and 7 came from nine sites classified according to location (LOC ) and type of vegetation (TYPE). (The data are given in Table 5.1.) Do the analysis of variance on BIOMASS partitioning the sum of squares into that due to LOC, TYPE, and LOC -by-TYPE interaction. The regression models in Chapter 7 indicated that pH and Na were important variables in accounting for the variation in BIOMASS. Add these two variables to your analysis of variance model as covariates (center each) and compute the analysis of covariance. Obtain the adjusted LOC, TYPE, and LOC -by-TYPE treatment means. Interpret the results of the covariance analysis. For what purpose is the analysis of covariance being used in this case?

Table 5.1