I have a question regarding the degree of freedom in the solution. Model 2 has 3 df, why? When I do it on my own I first calculate the parameters in that model, i.e. 4 +4-1=7. 4 parameters from Model 1= YO+FS+TC, Model 2 is YO+FS+TC+YO.FS, which is basically model 1 plus the interaction term. The interaction term has 4 parameters, that is 2*2=4. So the df=cells-parameters would be 8-7=1, but the solution says 3. Am I doing something wrong perhaps?
Yes YO*FS has 2*2=4 parameters whereas adding on an interactive term only YO.FS has (2-1)*(2-1) = 1 parameter. Or if you prefer model 2 is YO*FS + TC = 2*2 + (2-1) = 5 parameters. One more parameter than model 1 hence 1 less degree of freedom.
