Overall model test from Ordinal Logistic Regression

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dansquared
Posts: 4
Joined: Wed Dec 07, 2022 12:25 am

Overall model test from Ordinal Logistic Regression

Post by dansquared »

Hi all,
I'm exploring the ordinal regression analysis in Jamovi, and I'm wondering what's the Overall Model Test from Model Fit tab. Is it the same as the Score Test for the Proportional Odds Assumption from SAS?
overallmodeltest.png
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Thanks in advance!
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MAgojam
Posts: 421
Joined: Thu Jun 08, 2017 2:33 pm
Location: Parma (Italy)

Re: Overall model test from Ordinal Logistic Regression

Post by MAgojam »

Hey @dansquared,
as you surely know, under the hood of jamovi beats R.
Here, in the ordinal logistic regression sources, you find the call to the polr() function of the MASS package:
https://github.com/jamovi/jmv/blob/master/R/logregord.b.R#L63-L68

Description
Fits a logistic or probit regression model to an ordered factor response. The default logistic case is proportional odds logistic regression, after which the function is named.

Cheers,
Maurizio
dansquared
Posts: 4
Joined: Wed Dec 07, 2022 12:25 am

Re: Overall model test from Ordinal Logistic Regression

Post by dansquared »

Hey @MAgojam, thanks a lot for pointing me the code behind the ordinal regression, but I'm still having a hard time figuring out the Overall Model Test. It's testing against a null model, but what's this null model?
tegedik
Posts: 4
Joined: Thu Feb 15, 2018 6:20 pm

Re: Overall model test from Ordinal Logistic Regression

Post by tegedik »

Hello @dansquared, overall model test uses the likelihood ratio chi-square and it compares the full model against the null model with no predictors.
dansquared
Posts: 4
Joined: Wed Dec 07, 2022 12:25 am

Re: Overall model test from Ordinal Logistic Regression

Post by dansquared »

Hi @tegedik, oh I see! That makes sense, thanks!
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