bugPSPP - Bugs: bug #57722, Wrong results of NPAR TEST MCNEMAR...

 
 

bug #57722: Wrong results of NPAR TEST MCNEMAR for some data

Submitter:  None
Submitted:  Sun 02 Feb 2020 08:41:37 AM UTC
Votes: 50
 
Category:  Numerical Errors Severity:  5 - Average
Status:  Fixed Assigned to:  None
Open/Closed:  Closed Release:  None
Effort:  0.00
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Sun 02 Feb 2020 10:53:35 AM UTC, comment #1: 

Thank you for this bug report.

I have pushed a fix to the git repository.

John Darrington <jmd>
Group administrator
Sun 02 Feb 2020 08:41:37 AM UTC, original submission:  

The wrong results are the same in the two PSPP versions I have tested:
  * 1.2.0-3 on Debian Buster 64-bit;
  * pspp-20200117-daily-32bits-ForTestingOnly on Windows 7 64-bit.

Steps to reproduce:
1. Open the attached files mcnemar-bug.sav and mcnemar-bug.sps in PSPP.
2. Run all of mcnemar-bug.sps.

Actual results:

NPAR TEST
        /MCNEMAR var1 WITH  var2 (PAIRED).

var1 & var2
╔════╦═════╗
║var1║ var2║
║    ╟──┬──╢
║    ║0 │1 ║
╠════╬══╪══╣
║0   ║ 9│ 1║
║1   ║ 8│ 5║
╚════╩══╧══╝

Test Statistics
╔═══════════╤══╤═════════════════════╤═════════════════════╤
║           │ N│Exact Sig. (2-tailed)│Exact Sig. (1-tailed)│
╠═══════════╪══╪═════════════════════╪═════════════════════╪
║var1 & var2│23│                1.996│                 .998│
╚═══════════╧══╧═════════════════════╧═════════════════════╧

(this column didn't fit into the bug report field width) Point Probability: .02


NPAR TEST
        /MCNEMAR var2 WITH  var1 (PAIRED).

var2 & var1
╔════╦═════╗
║var2║ var1║
║    ╟──┬──╢
║    ║0 │1 ║
╠════╬══╪══╣
║0   ║ 9│ 8║
║1   ║ 1│ 5║
╚════╩══╧══╝

Test Statistics
╔═══════════╤══╤═════════════════════╤═════════════════════╤
║           │ N│Exact Sig. (2-tailed)│Exact Sig. (1-tailed)│
╠═══════════╪══╪═════════════════════╪═════════════════════╪
║var2 & var1│23│                 .039│                 .020│
╚═══════════╧══╧═════════════════════╧═════════════════════╧

(this column didn't fit into the bug report field width) Point Probability: .02

Expected results:
The second result may be correct - it is the same as the result of a sign test.
McNemar test is symmetrical, therefore the results must be identical when the variables are swapped. However both Exact Sigs differ. Moreover, in the first result Exact Sig. (2-tailed) is greater than 1, which is impossible because this is a probability value.

Anonymous

 

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Attach Files:
   
   
Comment:
   

Attached Files
file #48329:  mcnemar-bug.sav added by None (531B - application/x-spss-sav)
file #48330:  mcnemar-bug.sps added by None (93B - application/octet-stream)

 

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)
  • -email is unavailable- added by vedg (I have submitted this bug report before registering here.)
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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2020-02-02 jmd StatusNone Fixed
        Open/ClosedOpen Closed
    2020-02-02 vedg Carbon-Copy- Added vedg
    2020-02-02 None Attached File- Added mcnemar-bug.sav, #48329
        Attached File- Added mcnemar-bug.sps, #48330

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