bugPSPP - Bugs: bug #51146, Regression: r correlation...

 
 

bug #51146: Regression: r correlation coefficient sign error

Submitter:  None
Submitted:  Tue 30 May 2017 11:15:39 PM UTC
   
 
Category:  Numerical Errors Severity:  5 - Average
Status:  Invalid Assigned to:  None
Open/Closed:  Closed Release:  None
Effort:  0.00
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Thu 15 Jun 2017 02:52:30 PM UTC, comment #2: 

Closing as invalid.  If anyone thinks this is wrong.  Please re-open.

John Darrington <jmd>
Group administrator
Wed 31 May 2017 06:27:03 AM UTC, comment #1: 

I think you are referring to the "R" in the left hand column of the "Model Summary" box.  This is NOT the Pearson Correlation Coefficient.

It is nothing other than the square root of "R Square"  which is a measure of how much variance in the model is explained by the predictor variables.  Some authors call this "Multiple R^2".

In the special case of simple linear regression (when there is only one predictor variable) R does indeed have the same magnitude as that of the Pearson correlation coefficient, but it should not be regarded as the same value.

The coefficent "Beta" in your example is correctly given as -0.76
(-0.7556 if you increase the number of decimals in the output).

John Darrington <jmd>
Group administrator
Tue 30 May 2017 11:15:39 PM UTC, original submission:  

Hello:

In the example file I am attaching the correct result for the simple regression model is (as calculated using R):

y.hat = 0.5259 - 0.0001x

PSPP gives

y.hat = 0.53 + 0.00x

It might seem to be a matter of decimal digits, but main problem is PSPP gives the value of r (Pearson's correlation coefficient) as 0.76; but it is -0.76, so it has a problem with the sign of r and beta.hat1.

I am a teacher and this error pop up at my class yesterday. Could it be solved?

Anonymous

 

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Attached Files
file #40816:  Memoria.sav added by None (1KiB - application/x-spss-sav - Files of data, results and a Word file with results obtained using R)
file #40817:  Resultados PSPP Retencion de Memoria 2017 05 29.pdf added by None (46KiB - application/pdf - Files of data, results and a Word file with results obtained using R)
file #40818:  Ejemplo Retención de memoria.docx added by None (29KiB - application/vnd.openxmlformats-officedocument.wordprocessingml.document - Files of data, results and a Word file with results obtained using R)

 

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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2017-06-15 jmd StatusNone Invalid
        Open/ClosedOpen Closed
    2017-05-30 None Attached File- Added Memoria.sav, #40816
        Attached File- Added Resultados PSPP Retencion de Memoria 2017 05 29.pdf, #40817
        Attached File- Added Ejemplo Retención de memoria.docx, #40818

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