[R] testing diff for slopes and intercepts
wsi at gcal.ac.uk
Mon Oct 8 12:58:23 CEST 2001
I fit the model
thresh is the reponse
cond is a factor with levels a, b, and c
Ne is a continuous indep var
I think of this full model as having three lines: thresh as a function of
Ne for each condition. Thus we have slopea, slopeb, slopec, inta, intb,
lm output my params
condb intb - inta
condc intc - inta
condb:Ne slopeb - slopea
condc:Ne slopec - slopea
This parametrization automatically compares
inta vs intb
inta vs intc
But how to get test for diff of intb vs intc?
Same question for slope: I already have
slopea vs slopeb
slopea vs slopec
But how to get test for diff of slopeb vs slopec?
Thanks for any help.
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