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interpreting Std. error from glmer output

3 messages · Will Morris, Christine Griffiths, ONKELINX, Thierry

Original
Will Morris
# 
Well, it depends.

It depends on what you mean by deviance, you should clarify this (here  
is a start http://en.wikipedia.org/wiki/Deviance_%28statistics%29). In  
general, deviance is used as a measure of model fit and usually  
encountered as a component of Information criteria.

Do you need to take the uncertainty (SE) in model estimates into  
account? It is probably a good idea if you are going to make  
predictions based on model estimates to also calculate predictions at  
the 95CI limits.
On 15/09/2009, at 10:26 PM, Christine Griffiths wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
Will Morris
Masters of Philosophy candidate
Vesk Plant Ecology Lab
The School of Botany
The University of Melbourne
Australia
Phone: +61 3 8344 0120
http://www.botany.unimelb.edu.au/vesk/

  
  


  


    

    

      
      

        


  

        

      Christine Griffiths
    

    

      
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Thank you for your help. Because I am using glmer with Binomial family I 
cannot calculate 95% CIs using the mcmcsamp function and have not been able 
to find a way to do this. Hence my reason to look at the SE.

I probably didn't explain myself clearly enough. What I meant is, is the SE 
for a fixed effect the difference from the intercept, just as the mean for 
a fixed effect needs to be calculated as a difference from the intercept?
Your definition earlier seemed to support that it is a difference and so I 
need to calculate the SE by summing the value given with the intercept.

        
--On 15 September 2009 23:32 +1000 William Morris <wkmor1 at gmail.com> wrote:

        

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
----------------------
Christine Griffiths
PhD student
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG
Tel: 0117 9287593
Fax 0117 3317985
Christine.Griffiths at bristol.ac.uk
http://www.bio.bris.ac.uk/research/mammal/tortoises.html

  
  


  


      

    

    

      
      

        


  

        

      ONKELINX, Thierry
    

    

      
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Dear Christine,

Be carefull about that. The SE of a sum is NOT the sums of the SE! But
the variance of a sum is the sum of the variances minus the covariance.

The easiest option would be to refit the model without intercept if you
want the 'total' SE for each treatment.

HTH,

Thierry


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-sig-mixed-models-bounces at r-project.org
[mailto:r-sig-mixed-models-bounces at r-project.org] Namens Christine
Griffiths
Verzonden: dinsdag 15 september 2009 18:29
Aan: William Morris
CC: r-sig-mixed-models at r-project.org
Onderwerp: Re: [R-sig-ME] interpreting Std. error from glmer output

Thank you for your help. Because I am using glmer with Binomial family I
cannot calculate 95% CIs using the mcmcsamp function and have not been
able to find a way to do this. Hence my reason to look at the SE.

I probably didn't explain myself clearly enough. What I meant is, is the
SE for a fixed effect the difference from the intercept, just as the
mean for a fixed effect needs to be calculated as a difference from the
intercept?
Your definition earlier seemed to support that it is a difference and so
I need to calculate the SE by summing the value given with the
intercept.

--On 15 September 2009 23:32 +1000 William Morris <wkmor1 at gmail.com>
wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
----------------------
Christine Griffiths
PhD student
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG
Tel: 0117 9287593
Fax 0117 3317985
Christine.Griffiths at bristol.ac.uk
http://www.bio.bris.ac.uk/research/mammal/tortoises.html

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