Dear all,

 

I have fitted two glmer models (with or without intercept term). I
thought the results should be similar if not identical, but they are
quite different. I suspect it's related to the random effects. Any
suggestions on how to proceed is greatly appreciated.

 

Kind regards,

Ruby Chang

 

fit1 <- glmer(Cyptoplasmic.vacuolation ~ Group +  (1|Villus) +
(1|Cell),family=binomial(link = "logit"))

fit2 <- glmer(Cyptoplasmic.vacuolation ~ Group -1 +  (1|Villus) +
(1|Cell),family=binomial(link = "logit"))

 

> table(Cyptoplasmic.vacuolation, Group)

                        Group

Cyptoplasmic.vacuolation Capsule 1 Capsule 2 Control

                       0       560       340    1230

                       1       190       160      20

 

> fit1 <- glmer(Cyptoplasmic.vacuolation ~ Group +  (1|Villus) +
(1|Cell),family=binomial(link = "logit"))

> summary(fit1)

Generalized linear mixed model fit by the Laplace approximation 

Formula: Cyptoplasmic.vacuolation ~ Group + (1 | Villus) + (1 | Cell) 

   AIC   BIC logLik deviance

 138.9 168.1 -64.47    128.9

Random effects:

 Groups Name        Variance  Std.Dev.

 Cell   (Intercept) 1983.5708 44.5373 

 Villus (Intercept)    5.9475  2.4387 

Number of obs: 2500, groups: Cell, 250; Villus, 50

 

Fixed effects:

               Estimate Std. Error z value Pr(>|z|)

(Intercept)     -11.945      9.123  -1.309    0.190

GroupCapsule 2   -1.409     14.343  -0.098    0.922

GroupControl    -17.792     33.251  -0.535    0.593

 

Correlation of Fixed Effects:

            (Intr) GrpCp2

GroupCapsl2 -0.636       

GroupContrl -0.274  0.175

> fit2 <- glmer(Cyptoplasmic.vacuolation ~ Group -1 +  (1|Villus) +
(1|Cell),family=binomial(link = "logit"))

> summary(fit2)

Generalized linear mixed model fit by the Laplace approximation 

Formula: Cyptoplasmic.vacuolation ~ Group - 1 + (1 | Villus) + (1 |
Cell) 

   AIC   BIC logLik deviance

 132.9 162.0 -61.43    122.9

Random effects:

 Groups Name        Variance   Std.Dev.  

 Cell   (Intercept) 5.9933e+03 7.7417e+01

 Villus (Intercept) 1.2025e-07 3.4677e-04

Number of obs: 2500, groups: Cell, 250; Villus, 50

 

Fixed effects:

               Estimate Std. Error z value Pr(>|z|)

GroupCapsule 1   -15.08      17.70  -0.852    0.394

GroupCapsule 2   -14.72      19.29  -0.763    0.445

GroupControl     -18.23      54.54  -0.334    0.738

 

Correlation of Fixed Effects:

            GrpCp1 GrpCp2

GroupCapsl2 0.000        

GroupContrl 0.000  0.000


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