[R-sig-ME] comparing 3 levels of fixed factor in lme4

John Maindonald john.maindonald at anu.edu.au
Mon Jul 30 13:00:18 CEST 2012

Perhaps Andrew has vaguely at the back of his mind the notion
that for comparing >2 means, one should be using a multiple
range test or an anova test, at all events if the aim is to achieve
an experiment-wise 5% level.  Tests based on the individual
t-statistics are not independent.  This is of course a somewhat
controversial area.  
John Maindonald             email: john.maindonald at anu.edu.au
phone : +61 2 (6125)3473    fax  : +61 2(6125)5549
Centre for Mathematics & Its Applications, Room 1194,
John Dedman Mathematical Sciences Building (Building 27)
Australian National University, Canberra ACT 0200.

On 30/07/2012, at 8:38 PM, peter dalgaard wrote:

> On Jul 30, 2012, at 08:04 , Obermeier Andrew wrote:
>> In lme4, in models with 3 levels of the fixed factor, each of these gets a t value comparing it to a reference level.
>> How is this done? 
>> It is my understanding that the t value can only be used to compare 2 means.
> Then your understanding is wrong, and you need to read a text on basic linear modelling theory. Nothing specifically mixed-model or even R relevant about that.
> -- 
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com
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