Sven-Erik
This is a rather crude program I wrote that does Scheffe pairwise
comparisons for a oneway repeated design. The calling sequence would be
schefrpm y sub treat
where `y' is the dependent variable, `sub' is the random factor that is
repeated and `treat' is a fixed treatment factor. The model is given as a
comment in the program below. WHen you run this program you get:
1. The ANOVA output
2. A list of treatment means and est. sd's
3. A list of all pairwise comparisons with adjusted F and and P-values. For
example
3 2 -0.21 0.5349
means the comparison of level 3 with level 2 of the treatment factor, the
F-value was -0.21 and the P-value was 0.5349.
4. There is a bunch of other stuff, like degrees of freedom stored in
scalars.
program define schefrpm
/* Scheffe contrast tests for repeated measures design
yij = u + ai + bej + eij
ai = random subject effect
bj = fixed treatment effect */
/* `1' is dep; `2' is subjects; `3' is treatments */
version 5.0
anova `1' `2' `3'
scalar s2 = e(rss)/e(df_r) /* _result(4)/_result(5) */
local df2=e(df_r) /* _result(5) */
qui tab `3'
scalar k = r(r) /* number of treatments */
local k=scalar(k)
preserve
collapse (mean) y=`1' (count) n=`1' (sd) sd=`1' ,by(`3')
label var y "average"
format y sd %8.2f
list
local i=0
while `i' < `k' {
local i=`i' + 1
local j=0
while `j' < `i'-1 {
local j=`j'+1
scal dif=y[`i']-y[`j']
scal var=s2*(1/n[`i']+1/n[`j'])
scal t2=dif*dif/var
local F=t2/(`k'-1)
local df1=`k'-1
scal F`i'`j'=`F'
scal df1`i'`j'=`df1'
scal df2`i'`j'=`df2'
scal P`i'`j' = fprob(`df1',`df2',`F')
di `i' " " `j' " " %8.2f dif " " %8.4f P`i'`j'
}
}
restore
end
Hopefully, this could be of some use to you.
AL Feiveson
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