Dear list members,

I am trying to fit a linear mixed model using the following variables::

Response variable:

Swiftness.2 (This is the time it took for the otter to first approach 
the lure.  The time ranges from 1 second (in which case the otter 
approached the lure almost immediately) to 600 seconds (10 minutes).

Explanatory variables:
1) Subject (this is the individual otter -- each otter is measured for 
response to each lure, so it is a repeated measure on the individual);
2) sex;
3)  facility size (small, med, large);
4) lure type (there were 6).

I would like to see if the response variable is influenced by the 
explanatory variables including Subject like a "repeated measure" term 
(same animal expose to different lures).

I am fitting the model:

otter$Facility.Size = factor(otter$Facility.Size)
otter$Sex = factor(otter$Sex)

mod1 = lmer(Swiftness.1 ~ Lure + Sex + Facility.Size + (1|Subject), data 
= otter)
summary(mod1)

 > mod1 = lmer(Swiftness.1 ~ Lure + Sex + Facility.Size + (1|Subject), 
data = otter)
 > summary(mod1)
Linear mixed model fit by REML
Formula: Swiftness.1 ~ Lure + Sex + Facility.Size + (1 | Subject)
    Data: otter
   AIC  BIC logLik deviance REMLdev
  1277 1295 -631.3     1302    1263
Random effects:
  Groups   Name        Variance Std.Dev.
  Subject  (Intercept)     0      0.00
  Residual             21558    146.83
Number of obs: 102, groups: Subject, 17

Fixed effects:
                Estimate Std. Error t value
(Intercept)      92.883     44.711   2.077
Lure             -6.286      8.513  -0.738
Sex1             -3.266     29.199  -0.112
Facility.Size2   24.174     37.628   0.642
Facility.Size3   58.528     38.692   1.513

Correlation of Fixed Effects:
             (Intr) Lure   Sex1   Fcl.S2
Lure        -0.666
Sex1        -0.327  0.000
Facilty.Sz2 -0.516  0.000 -0.055
Facilty.Sz3 -0.519  0.000  0.000  0.617


Is the model a plausible model and is it well parameterized?

Best,

Manuel

-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspinola@una.ac.cr
mspinola10@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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