[R-sig-ME] Residuals plot for a linear mixed model

[Manuel Spínola]

Dear list members,

I got the attached residuals plot for linear mixed model after 
logtransformationn of the response variable.
Is the plot telling me that I have a problem with the model fitted?  If 
logtransformation didn't help, what are thealternatives?

 > mode = lmer(log(Swiftness.1 + 0.05) ~ Lure + Sex + Facility.Size + 
(1|Subject), REML = F, data = otter)
 > summary(mode)
Linear mixed model fit by maximum likelihood
Formula: log(Swiftness.1 + 0.05) ~ Lure + Sex + Facility.Size + (1 | 
Subject)
    Data: otter
  AIC   BIC logLik deviance REMLdev
  546 574.9   -262      524   511.5
Random effects:
  Groups   Name        Variance Std.Dev.
  Subject  (Intercept) 0.75907  0.87125
  Residual             9.33305  3.05500
Number of obs: 102, groups: Subject, 17

Fixed effects:
                    Estimate Std. Error t value
(Intercept)          1.1968     1.0832   1.105
Lure[T.2]           -0.4375     1.0479  -0.418
Lure[T.3]            0.9928     1.0479   0.947
Lure[T.4]            0.4381     1.0479   0.418
Lure[T.5]           -0.3059     1.0479  -0.292
Lure[T.6]           -1.1340     1.0479  -1.082
Sex[T.1]            -0.2301     0.7411  -0.311
Facility.Size[T.2]   1.9357     0.9550   2.027
Facility.Size[T.3]   1.2889     0.9820   1.312

Correlation of Fixed Effects:
             (Intr) L[T.2] L[T.3] L[T.4] L[T.5] L[T.6] S[T.1] F.S[T.2
Lure[T.2]   -0.484
Lure[T.3]   -0.484  0.500
Lure[T.4]   -0.484  0.500  0.500
Lure[T.5]   -0.484  0.500  0.500  0.500
Lure[T.6]   -0.484  0.500  0.500  0.500  0.500
Sex[T.1]    -0.342  0.000  0.000  0.000  0.000  0.000
Fclt.S[T.2] -0.540  0.000  0.000  0.000  0.000  0.000 -0.055
Fclt.S[T.3] -0.544  0.000  0.000  0.000  0.000  0.000  0.000  0.617

predicted<-fitted(mode)
raw.residuals<-residuals(mode)
plot(predicted,raw.residuals)
abline(h=c(-1.96*sd(raw.residuals),0,1.96*sd(raw.residuals)))


Best,

Manuel



-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspinola at una.ac.cr
mspinola10 at gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 
<https://sites.google.com/site/lobitoderio/>
Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/>
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