Hello r helpers! Below is the whole coding for my programme. Before proceed
more further, let me explain for you. First of all, I need to compute trimmed
mean. Till that step is ok. Then I need to compute ssdw which is sum of square
deviation. If I do equal trimming at both tail of distribution that I chose, I
will use the first ssd formulae which is "a". But if I am doing unequal
trimming, then I will be using "b". My problem is I dont know how to come out
with a value of ssdw. For example, if the value of gw1=gw2 (which mean equal
trimming), the result will come out as "a" not the value of ssdw when equal
trimming is done. I f anyone could with this, I really appreciate it. I need
the value of ssdw so that I can proceed with computing the F test. Thanks.
Regards,
Hyo Min
UPM Malaysia
n1<-15
miu<-0
sd1<-1
data1<-rnorm(n1,miu,sd1)
## data transformation as G=0.5 and h=0.5 (data is normal)
G<-0.5
h<-0.5
w<-((exp(G*data1)-1)/G)*(exp((h*data1^2)/2))
group1<-sort(w)
g<-0.15 ## proportion of trimming
## group 1
uw<-floor(0.2*n1)
low1<-mean(group1[1:uw])
uppw1<-mean(group1[(n1-uw+1):n1])
UWx<-uppw1-low1
vw<-floor(0.5*n1)
low2<-mean(group1[1:vw])
uppw2<-mean(group1[(n1-vw+1):n1])
LWx<-uppw2-low2
gam.low<-g*(UWx/(UWx+LWx))
gam.upp<-g-gam.low
gw1<-floor(n1*gam.low)
gw2<-floor(n1*gam.upp)
hw<-n1-gw1-gw2
trim.mean1<-1/hw*(sum(group1[(gw1+1):(n1-gw2)]))
a<-((gw1+1)*((group1[gw1+1]-trim.mean1)^2))+sum(group1[(gw1+2):(n1-gw1-1)]-trim.mean1)^2+((gw1+1)*(group1[n1-gw1]-trim.mean1)^2)
b<-(((gw1+1)*((group1[gw1+1]-trim.mean1)^2))+sum(group1[(gw1+2):(n1-gw2-1)]-trim.mean1)^2+((gw2+1)*(group1[n1-gw2]-trim.mean1)^2)-(gw1*(group1[gw1+1]-trim.mean1)+gw2*(group1[n1-gw2]-trim.mean1)^2))/n1
ssdw<-ifelse(gw1==gw2, "a", "b")
ssdw
## calculate Ft test statistic
H<-hw
C<-1
A<-hw*trim.mean1
xbar<-A/H
X<-hw*(trim.mean1-xbar)^2
Y<-ssdw
df1<-1
df2<-H-C
upper<-X/df1
lower<-Y/df2
Ft<-upper/lower
Ft
pv<-1-pf(Ft,df1,df2)
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