Hello Christian,

Thanks for your input.  I tried the changes that you suggested and it
actually did yield a different result from our original model specification
(please see below).

-Austen


> # LME for Dive Depth Focus (DDF)
> #For lme4 package
> #summary(d)
> lmer(DDF~Season*Period+(1|Seal/Season/Period), data=d, REML=F)->fit10
> #summary(fit10)
> lmer(DDF~Season+Period+(1|Seal/Season/Period), data=d, REML=F)->fit11
> lmer(DDF~Season+(1|Seal/Season/Period), data=d, REML=F)->fit12
> lmer(DDF~1+(1|Seal/Season/Period), data=d, REML=F)->fit13
> anova(fit10, fit11, fit12, fit13)
Data: d
Models:
fit13: DDF ~ 1 + (1 | Seal/Season/Period)
fit12: DDF ~ Season + (1 | Seal/Season/Period)
fit11: DDF ~ Season + Period + (1 | Seal/Season/Period)
fit10: DDF ~ Season * Period + (1 | Seal/Season/Period)
      Df     AIC     BIC  logLik  Chisq Chi Df Pr(>Chisq)
fit13  5 -48.958 -23.951  29.479
fit12  6 -47.799 -17.792  29.900 0.8416      1    0.35894
fit11  9 -47.515  -2.504  32.758 5.7161      3    0.12627
fit10 12 -50.398   9.617  37.199 8.8826      3    0.03089 *
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1


> # LME for Dive Depth Focus (DDF)
> #For lme4 package
> #summary(d)
> lmer(DDF~Season*Period+(1|Seal:Season:Period), data=d, REML=F)->fit10
> #summary(fit10)
> lmer(DDF~Season+Period+(1|Seal:Season:Period), data=d, REML=F)->fit11
> lmer(DDF~Season+(1|Seal:Season:Period), data=d, REML=F)->fit12
> lmer(DDF~1+(1|Seal:Season:Period), data=d, REML=F)->fit13
> anova(fit10, fit11, fit12, fit13)
Data: d
Models:
fit13: DDF ~ 1 + (1 | Seal:Season:Period)
fit12: DDF ~ Season + (1 | Seal:Season:Period)
fit11: DDF ~ Season + Period + (1 | Seal:Season:Period)
fit10: DDF ~ Season * Period + (1 | Seal:Season:Period)
      Df     AIC     BIC  logLik  Chisq Chi Df Pr(>Chisq)
fit13  3 -47.837 -32.833  26.918
fit12  4 -47.246 -27.242  27.623 1.4095      1     0.2351
fit11  7 -44.909  -9.900  29.455 3.6625      3     0.3003
fit10 10 -44.166   5.847  32.083 5.2565      3     0.1539



On Wed, Jan 27, 2010 at 11:29 PM, Christian Ritz <ritz@life.ku.dk> wrote:

> Hi Austen,
>
> apart from the residual error I could imagine that there are two additional
> layers of
> variation in the experimental setup you've:
>
> (1|seal) - variation between seals
>
> (1|seal:season) - season-specific seal variation
>
> (1|seal:season:period) - season- and period-specific seal variation
>
>
> Far from sure that all sources will show up for an experiment only
> involving 5 seals. For
> clarity, I would prefer using these three terms to using
> "(1|seal/season/period)", even
> though I think the end result is this same as the latter is equivalent to:
>
> (1|seal) + (1|seal:season) + (1|seal:season:period)
>
>
> If there are no replicates (you didn't tell us about replicates...) the
> last term will be
> redundant as it corresponds to the residual error term, which is anyway
> part of the model.
> So in short your original model specification looks ok to me.
>
>
> Christian
>
>


-- 
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Western Washington University
Biology Building BI 315
Mail Stop 9160
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