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Andrew_Botfield
Andrew_Botfield
Level II

Can you display R squared value with Bi-variate fit special and forcing intercept through y = 0?

Created: Jul 17, 2020 12:52 AM  |  Last Modified: Jun 11, 2023 5:04 AM (1567 views)
 
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2 REPLIES 2
Byron_JMP
Staff Byron_JMP
Staff

Re: Can you display R squared value with Bi-variate fit special and forcing intercept through y = 0?

Created: Sep 22, 2020 10:00 AM  |  Last Modified: Sep 22, 2020 11:36 AM (1408 views)  |  Posted in reply to message from Andrew_Botfield 07-17-2020

Yes, but No.  Use the Fit Special option

 

Screen Shot 2020-09-22 at 9.57.14 AM.png

 

Screen Shot 2020-09-22 at 2.29.36 PM.png

 

(earlier I added the wrong screen shot)

The thing is, when you fix the slope or intercept, then you're not really doing a least squared fit.

Since RSquare is the sum of squares for the model divided by the total sum of squares, there isn't exactly a model to work with for the fit.

JMP Systems Engineer, Health and Life Sciences (Pharma)
Dan_Obermiller
Staff Dan_Obermiller
Staff

Re: Can you display R squared value with Bi-variate fit special and forcing intercept through y = 0?

Created: Sep 22, 2020 02:23 PM  |  Last Modified: Sep 22, 2020 4:58 PM (1396 views)  |  Posted in reply to message from Byron_JMP 09-22-2020

Caution! Care must be taken when interpreting an RSquare value with the intercept forced to be 0. The usual statistics like RSquare assume that you are using the mean of the response (Y-bar) for your sums of squares. By forcing the intercept to be 0, you are replacing Y-bar with 0. This alters the typical interpretations of those statistics. How much is altered will depend on how far your Y-bar is from 0.

For example, it is possible to achieve a negative RSquare value when you constrain the intercept to 0. For this reason, most people are in favor of not reporting RSquare in such cases.

Dan Obermiller