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

[Becky Gilbert]

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

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