Thank you very much Ben.

Best,

Manuel

On 19/03/2011 09:54 a.m., Ben Bolker wrote:
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> On 11-03-19 11:27 AM, Manuel Spínola wrote:
>> Thank you very much Ben,
>>
>> I decided to keep "otter" as a random factor:
>>
>> modA = lmer(Swiftness.1 ~ Lure + Sex + Facility.Size + (1|Subject), REML
>> = F, data = otter)
>> summary(modA)
>>
>> modB = lmer(Swiftness.1 ~ (1|Subject), REML = F, data = otter)
>> summary(modB)
>>
>> modC = lmer(Swiftness.1 ~ Lure + (1|Subject), REML = F, data = otter)
>> summary(modC)
>>
>>> AICctab(modA, modB, modC, weights = T, delta = TRUE, base = T, sort =
>> TRUE, nobs = 17)
>>       AICc   df dAICc  weight
>> modB 1313.1 3     0.0 1
>> modC 1336.3 8    23.2<0.001
>> modA 1374.5 11   61.4<0.001
>>
>> Output for best model:
>>
>>> summary(modB)
>> Linear mixed model fit by maximum likelihood
>> Formula: Swiftness.1 ~ (1 | Subject)
>>     Data: otter
>>    AIC  BIC logLik deviance REMLdev
>>   1311 1319 -652.6     1305    1298
>> Random effects:
>>   Groups   Name        Variance Std.Dev.
>>   Subject  (Intercept)     0      0.00
>>   Residual             21133    145.37
>> Number of obs: 102, groups: Subject, 17
>>
>> Fixed effects:
>>              Estimate Std. Error t value
>> (Intercept)    99.76      14.39   6.931
>>
>>
>> Is it fair to say that there is no effect of any of the factors?
>> Did you say that the variance 0 in the random effect output is low power?
>>
>    Yes, although technically I would say that the factors are not useful
> for prediction; if you want to test for the presence of a significant
> effect, then fit the full model and report the p-values and confidence
> intervals from it.  Yes, I would say that the zero variance represents
> noise/ low power: if you were to do the equivalent aov()-analysis it
> would probably report a negative variance (i.e., among-group mean square
> <  within-group mean square).
>
>    Ben
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-- 
*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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