COOCHE@QUCDN.BITNET (Evan G. Cooch) (02/07/90)
This is cross-listed with STAT-L...
I realize that this is historically a thorny issue, but what the heck...
In a number of recent queries, I have dealt with various means of using SAS
to do something analogous to paired-slopes comparisons. A number of
correspondnets at that time suggested that such estimates would have to
be adjusted (using Bonferroni, or Sidak etc) to reduce the error.
However, this would seem to me to be appropriate if I was A PRIORI
deciding to test (say) slope A vs C alone. But in general, when I
have significant heterogeneity in slopes (significant CLASS*X term),
I'm not particularly interested in A PRIORI testing any two slopes,
but A POSTERIORI testing ALL slopes to see which ones are different
from which other ones. In simple ANOVA, I would use Tukey-Kramer, or
something analogous.
Given that paired-slopes testing is not typically a standard procedure,
are A PRIORI adjustments appropriate? If so, how (and what) do you adjust
in the tests?
My gut feeling is that since I'm testing everything, such adjustments may
be unecessary.
ANy suggestions would be appreciated...
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--(\=/)-- ( ) | Evan G. Cooch |
/ \ / / | Department of Biology |
I V / | Queen's University |
I / | Kingston, Ontario, Canada |
I / | (613-545-6129) |
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