PSPP-BUG: [bug #46749] logistic regression function having problems with categorical variables

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?46749>

                 Summary: logistic regression function having problems with
categorical variables
                 Project: PSPP
            Submitted by: None
            Submitted on: Tue 22 Dec 2015 01:52:06 PM UTC
                Category: None
                Severity: 5 - Average
                  Status: None
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                 Release: None
                  Effort: 0.00

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Details:

short description: while doing the logistic regression, pspp completely
ignores "measure" of the variable. it is treating categorical variable as a
continuous variable leading to wrong results.

complete description:
1) for reporting this, i am using the example given in this SPSS tutorial-
http://www.ats.ucla.edu/stat/spss/dae/logit.htm
2) look at the example dataset - binary.sav
3) open the file.
4) it contains four variables. two nominal (admit and rank) and two scale (gre
and gpa)[visible in the "measure" of variable view].
5)go to: analyse -> regression-> logistic regression
6)select admit as the dependent variable and rank,gre and gpa as the
independent variable.


expected result: the output should look like this -
http://i.imgur.com/W5Q4lTI.png

actual result in pspp: http://i.imgur.com/IEyOUnO.png

7) possible reason: pspp ignores the measure indicator of the variable. it
treats rank as a continuous variable.

8) this is a long term problem and it exists since the function is available
in pspp. did not report it as was unable to confirm the expected result from
SPSS.

9) interestingly, if this file is imported in R and logistic regression
analysis done, expected result takes place.


pspp version: 

psppire 0.8.5 (problem present since logistic regression function added in
PSPP)

system information (uname -a):

Linux 4.2.0-21-generic #25~14.04.1-Ubuntu SMP Thu Dec 3 13:55:58 UTC 2015
x86_64 x86_64 x86_64 GNU/Linux




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Date: Tue 22 Dec 2015 01:52:06 PM UTC  Name: W5Q4lTI.png  Size: 29kB   By:
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