why is it necessary to add a linear term and a quadratic term to a mixed model? why is it important to include the quadratic term in a linear model when you add a linear term to a mixed model, what is the difference is it better to have a linear term and a quadratic term in a mixed model can you add only the quadratic term to the mixed model what is quadratic and linear terms how many quadratic variables are needed to fit a mixed model does adding the quadratic term to the model make sense do quadratic and higher order polynomials make sense is it ok to add a quadratic term to mixed models why do you add a quadratic term to a mixed model when should i insert the linear term why does a mixed model not include a linear term why not include the linear and quadratic term in a mixed model do you need to add a quadratic term to a model? why is it important to add a linear and quadratic term in a mixed model why add a quadratic term to a model do you put a quadratic and a linear term in an experiment does it make sense to add a higher polynomial to a mixed model how many quadratic terms to add to a mixed model