[R-sig-ME] chisq = 0 and p = 1 in glmer model comparison result

[Guillaume Adeux]

Hello Becky,

Even though I cannot directly answer your question... a Chisq of 0 with
such a difference in AIC seems indeed suspicious.

To test the effect of your predictor in a GLMM context through LRT tests,
you could (should?) consider using the test_terms function from the {monet}
package or its little brother function mixed() from the {afex} package.
These packages are specifically designed for such tests.

I hope this helps.

Sincerely,

Guillaume ADEUX



Le lun. 3 juin 2019 à 15:14, Becky Gilbert <beckyannegilbert using gmail.com> a
écrit :

> Dear list
>
> I have two glmer models, one with a fixed factor (targetWordFactor) and one
> without, and I am comparing them using the anova function to get the LRT
> results for the fixed effect of targetWordFactor. The anova results are
> showing a chi-square value of 0 and p value of 1. Is this result possible,
> or is it perhaps a sign that I've done something wrong?
>
> Here are the anova results:
>
> anova(accModelNullWord,accModelWord)
> #                                  Df    AIC    BIC logLik deviance Chisq
> Chi Df Pr(>Chisq)
> # accModelNullWord 13 977.59 1067.0 -475.8   951.59
> # accModelWord       15 990.61 1093.8 -480.3   960.61     0      2
>  1
>
> The targetWordFactor fixed factor has 3 levels (2 contrasts), so the
> degrees of freedom in the anova result look correct to me. Here are the
> model specifications:
>
> contrasts(pauseDetValidNoFillersExcluded$targetWordFactor)
> #        WW NW
> # W       0  0
> # WW   1  0
> # NW    0  1
>
> accModelNullWord <- glmer(correct ~ 1 +
>                             (1 + targetWordFactor|subject) +
>                             (1 + targetWordFactor|item),
>                             data = pauseDetValidNoFillersExcluded,
>                             family = binomial(link = "logit"),
>                             control = glmerControl(optimizer="bobyqa",
>                                                  optCtrl =
> list(maxfun=2e5)))
>
> accModelWord <- glmer(correct ~ 1 + targetWordFactor +
>                         (1 + targetWordFactor|subject) +
>                         (1 + targetWordFactor|item),
>                         data = pauseDetValidNoFillersExcluded,
>                         family = binomial(link = "logit"),
>                         control = glmerControl(optimizer="bobyqa",
>                                              optCtrl = list(maxfun=2e5)))
>
> Apologies if this question has been asked before - I did search the list
> but couldn't find anything.
>
> Many thanks,
> Becky
>
>         [[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-mixed-models using r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>

	[[alternative HTML version deleted]]