Ricardo Ovaldia wrote:
Thank you again. One more question please. I have
another outcome in this experiment which is a
percentage ranging from 0 to 50, would it make sense
to use -gllamm- with a Gaussian family and an identity
link. Or is there a better way.
--------------------------------------------------------------------------------
If you want to fit normal mixed models, then -xtreg- or -xtmixed- would be
better choices: -xi: xtreg percentage i.culture_medium, i(dam)-. The
untransformed response variable might not be adequately normal-like for this,
so be sure to do the diagnostic plots.
-npt_s- (or -vanelteren-) would still be appropriate, though, if your interest
is in hypothesis testing.
Joseph Coveney
P.S. About my previous post in this thread: I've noticed that -npt_s- doesn't
correct for ties when performing stratified analysis, so I don't recommend it
now for the ordered-categorical response variable (at least until it gets
fixed--I'll send an e-mail message to Peter Sasieni). Use -vanelteren-
instead. The syntax for -vanelteren- is identical: -vanelteren embryo_grade,
by(culture_medium) strata(dam)-. Either -npt_s- or -vanelteren- will be fine
for the percentage response variable above, provided there are few, if any,
ties. If there are a substantial number of ties, then use -vanelteren- here,
too, which corrects for ties. Once -npt_s- is fixed to correct for ties in
stratified analysis, then it will render -vanelteren- superfluous, because
-npt_s- subsumes the latter's functionality.
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