Hello,
When I perform a quadratic regression, it returns the form y=a+bx+c(x-d)^2. I would like it in the form y=a+bx+cx^2 so that I can have the correct parameter estimates. How can I do this - either change the way the model returns or change the parameters as needed?
Thanks,
Brian
Hi, Brian!
Try using the Fit Special... dialog of the Fit Y by X platform (Under the LIRT by Bivariate Fit).
Leave both Y and X as No Transformation, specify the degree as 2 Quadratic, and uncheck the Centered Polynomial checkbox. That will give you the model you seek.
As an aside, JMP almost always centers the variables in analyses since it makes a lot of statistical sense (makes parameters comparable, etc.).
As another, more distant, aside LIRT stands for Little Inverted Red Triangle.
Hi, Brian!
Try using the Fit Special... dialog of the Fit Y by X platform (Under the LIRT by Bivariate Fit).
Leave both Y and X as No Transformation, specify the degree as 2 Quadratic, and uncheck the Centered Polynomial checkbox. That will give you the model you seek.
As an aside, JMP almost always centers the variables in analyses since it makes a lot of statistical sense (makes parameters comparable, etc.).
As another, more distant, aside LIRT stands for Little Inverted Red Triangle.
Thanks Kevin! Exactly what I was looking for!