I have conducted some ordinal logistic regressions, however, some of my tests have not met the proportional odds assumptions so I need to run multinomial regressions. What would I have to do to the ordinal DV to use it in this model? I'm doing this in SPSS by the way.
Hello Hannah Belcher. How did you determine that the proportional odds (aka., parallel lines) assumption was too severely violated? And what is your sample size?
I ask those questions, because the test of proportional odds is known to be too liberal (i.e., it rejects the null too easily), particularly as n increases. You can find some relevant discussion of this (and many other issues) in this nice tutorial:
- https://www.restore.ac.uk/srme/www/fac/soc/wie/research-new/srme/modules/mod5/index.html
HTH.
PS- If you do eventually decide that you need to estimate a multinomial logistic regression model, you do not have to do anything to the outcome variable. The NOMREG command will automatically treat it as nominal.
- https://www.ibm.com/docs/en/spss-statistics/28.0.0?topic=nomreg-overview-command
Hi Hannah,
First, note that there are several other models than proportionnal odds ratio model for ordinal logistic regression (see for instance Agresti books). In particular, the adjacent constant odds-ratio model which is mathematically equivalent to the multinomial regression. Most of these models, in contrary to the usual one, do not become inconsistent [probabilities 1] when proportional odds ratio assumption is not met.
So may be, another kind of ordinal logistic regression model is a better choice than directly going into multinomial regression?
For the reader only
You can perform proportional odds assumptions using the Test of parallel lines in the SPSS software.
1. You can see how to use ordinal logistic regression in the SPSS in the link below.
https://graphpad.ir/ordinal-logistic-regression-spss/
2. Multinomial logistic regression (SPSS)
https://graphpad.ir/multinomial-logistic-regression-spss/
3. Ordinal logistic regression (Minitab)
https://graphpad.ir/ordinal-logistic-regression-minitab/
4. Nominal logistic regression (Minitab)
https://graphpad.ir/nominal-logistic-regression-minitab/
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