[R-sig-ME] Jointly testing several parameters of factor variable

[Stijn Ruiter]

Hi all,
I am estimating a lmer model and now I would like to test whether some 
coefficients for specific levels of factor variable are equal.
I am thinking of either:
(1) applying equality constraints on several parameters for specific 
levels of a factor variable (and use that to do LRT against model 
without equality constraints), but I have no clue on how to that; or
(2) do a Wald test in which several parameter estimates of a factor 
variable are jointly tested. Although I noticed "wald.test" from the 
"aod" package, but I don't quite follow how to apply that to my lmer model.

Any suggestions on how to jointly test several parameters of a lmer 
model (preferably applied to factor variables)?

Stijn

-- 
Best regards,

Stijn Ruiter
Department of Sociology / ICS
Radboud University Nijmegen
P.O. Box 9104
6500 HE Nijmegen
Netherlands

Phone: + 31 24 361 2272
Fax:   + 31 24 361 2399

Visiting address:
Thomas van Aquinostraat 4.01.71
Nijmegen

website: http://oase.uci.ru.nl/~sruiter