R help - Mar 2005 - Question about Tukey HSD (stat package)

Dear all,

I would be glad if someone could tell me if Tukey HSD (function of stats 
library) accept the NA values and could correct the unbalanced design 
(different number of sample in each group)

Thanks for help

Alice Le Bars

Alice Le Bars <alice.le-bars at nantes.inserm.fr> writes:
> Dear all,
> 
> I would be glad if someone could tell me if Tukey HSD (function of
> stats library) accept the NA values and could correct the unbalanced
> design (different number of sample in each group)
I don't think the *theory* of the HSD allows this. There is some more
or less well-founded speculation that if the imbalance is not too bad,
then the HSD results are somewhat useful anyway, but please consider
using the multcomp package, which is specifically designed to get
these things right.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

On 14 Mar 2005 at 16:13, Peter Dalgaard wrote:
> Alice Le Bars <alice.le-bars at nantes.inserm.fr> writes:
> 
> > Dear all,
> > 
> > I would be glad if someone could tell me if Tukey HSD (function of
> > stats library) accept the NA values and could correct the unbalanced
> > design (different number of sample in each group)
> 
> I don't think the *theory* of the HSD allows this. There is some more
> or less well-founded speculation that if the imbalance is not too bad,
> then the HSD results are somewhat useful anyway, but please consider
> using the multcomp package, which is specifically designed to get
> these things right.
> 
I believe that Hayter (JASA, 1984, 12, 61--75) proves that the so-called
Tukey-Kramer method is guarnateed to be conservative for
any set of cell sizes --- under the usual ANOVA model, of course.

---JRG



> -- 
>    O__  ---- Peter Dalgaard             Blegdamsvej 3  
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
> 
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John R. Gleason

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