bugPSPP - Bugs: bug #35420, Regression output round off problem

 
 

bug #35420: Regression output round off problem

Submitter:  None
Submitted:  Tue 31 Jan 2012 10:31:51 PM UTC
   
 
Category:  Numerical Errors Severity:  3 - Ordinary
Status:  Invalid Assigned to:  None
Open/Closed:  Closed Release:  None
Effort:  0.00
* Mandatory Fields

Add a New Comment Rich Markup
   

Fri 10 Feb 2012 01:43:06 PM UTC, comment #2: 

Closing, since nothing needs to be done.

John Darrington <jmd>
Group administrator
Wed 01 Feb 2012 07:48:38 AM UTC, comment #1: 

Thanks very much for the report.

The "incorrect" value in physiology.sav is intentional!   This file is used as an example in Section 5.2 (Data Screening and Transformation) of the User Manual.  It demonstrates how PSPP can be used to catch typical data entry errors such as this.

Regarding the rounding issue, you can increase the reported number of decimal places by issuing the command "SET FORMAT F20.6." at the top of your file (this example will set the default output to a width of 20 and a precision of 6 decimal places).  This is slightly different to how SPSS works.


John Darrington <jmd>
Group administrator
Tue 31 Jan 2012 10:31:51 PM UTC, original submission:  

  I was experimenting with the correlation and regression features using the physiology.sav file from the example folder. I noticed that the residual for the variable "weight" for case 38 was very large. I then noticed that the weight for this case was apparently incorrect - it was negative.

  I deleted the negative sign and ran the analysis again to see how much it improved.  I was alarmed to see that the second run produced a multiple R of 1.00.  Although the predictions improved, they are clearly not perfect.

  I ran the analysis in SPSS, and found that the R was .998 - which would round up to 1.00 (and the R square of .996 would also round up to 1.00).  Although 1.00 is technically correct, to two significant digits, I think that it's worth changing the output in cases like this - or printing a warning.

  I have included the modified .sav file.  RES1 and PRED1 were produced BEFORE I corrected the negative weight.  RES2 and PRED2 were produced with the modified file.  I have also included a pdf of the output file - the second run of the regression procedure was with the modified data file and shows the R of 1.00.

Anonymous

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:
   
   
Comment:
   

Attached Files
file #24946:  physiologyCorrected.sav added by None (3KiB - application/octet-stream)
file #24947:  physiologyCorrectedOutput.pdf added by None (35KiB - application/pdf)

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -email is unavailable- added by jmd (Posted a comment)
  •  

    There are 0 votes so far. Votes easily highlight which items people would like to see resolved in priority, independently of the priority of the item set by tracker managers.

    Only logged-in users can vote.

     

    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2012-02-10 jmd StatusNone Invalid
        Open/ClosedOpen Closed
    2012-02-01 jmd Severity5 - Average 3 - Ordinary
    2012-01-31 None Attached File- Added physiologyCorrected.sav, #24946
        Attached File- Added physiologyCorrectedOutput.pdf, #24947

    Back to the top

    Powered by Savane 3.13-f8d8.
    Corresponding source code