[R] Mixed models and missing p-value...

[Simon Blanchet]

Dear R-users,

I computed a simple mixed models which was:

         mod<-lmer(nb ~ site + (1|patelle),tr)

The output was:

Linear mixed-effects model fit by REML
Formula: nb ~ site + (1 | patelle)
    Data: tr
       AIC      BIC    logLik MLdeviance REMLdeviance
  1157.437 1168.686 -574.7184   1164.523     1149.437
Random effects:
  Groups   Name        Variance Std.Dev.
  patelle  (Intercept)  34.995   5.9157
  Residual             744.736  27.2899
# of obs: 123, groups: patelle, 33

Fixed effects:
             Estimate Std. Error t value
(Intercept)  60.3483     4.3929 13.7378
siteLCN     -20.1969     7.8070 -2.5870
siteLCS     -18.2154     6.1514 -2.9612

Correlation of Fixed Effects:
         (Intr) sitLCN
siteLCN -0.563
siteLCS -0.714  0.402

I don't understand why D.F. and p-values associated to the fixed-effects 
coefficients are missing.
Could anyone help me?

When I tried another model (mod2<-lmer(nb ~ site + 
(1|patelle),tr,family=poisson)), D.F. and p-values were given...

Thank you in advance.

Very sincerely, Simon



BLANCHET Simon
PhD student
Université Laval - Québec-Océan / CIRSA
Pavillon Alexandre-Vachon
Local 8022
Québec (Québec), Canada G1K 7P4
Téléphone : (418) 656-2131 poste 8022
courriel : simon.blanchet at giroq.ulaval.ca