Dear coleagues,
I wrote a script for a multiple comparisions
like Scheffe test, according Zar, JH. Biostatiscal Analysis
pg.196..
my data is fish larvae abundance with 4 tratments
month (with 12 levels), year (with 9 levels), station
of year (with 4 levels) and area (with 3 levels)
after an anova procedure i apply this:
Scheffe<-function(mxa,mxb,ms,na,nb,k,F){
# Scheffe test for multiple comparision
# where mxa is mean of A(month, year,station or area
# mxb is some but other treatment
# ms is mean square of anova results
# na is number of A sample nb is number
# of sample B, k is degree of freedon of
# of treatments and F is critical value to
# to compare
#if S > Scrit -reject H0 else S < Scrit -accept H0
SE<-sqrt(ms*(1/na+1/nb))
S<-abs(mxb-mxa)/SE
Scrit<-sqrt((k-1)*F)
if (S > Scrit) result<-c("rej H0") else result<-c("ac
H0")
return(cbind(S,Scrit,result))
}
Is there some errors??
Is possible find the F values in R??
Thanks for some help
Marcelo