[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## logistic regression having problems with categorical variables

**From**: |
dr soumalya ray |

**Subject**: |
logistic regression having problems with categorical variables |

**Date**: |
Sat, 19 Dec 2015 06:28:49 +0000 (UTC) |

hello friends,
i'd like to point out a problem present in the "logistic regression" function
of PSPP.
this is a problem stopping usage of PSPP for logistic regression analysis.
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)
uname -a:Linux som 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
regards,
som

[Prev in Thread] |
**Current Thread** |
[Next in Thread] |

**logistic regression having problems with categorical variables**,
*dr soumalya ray* **<=**