#Biostatistics 150

#ZAR EXAMPLE 9.1
ZAR=read.table("ZarEX9.1.txt")
ZAR
attach(ZAR)
X1=hindlen
X2=forlen
d=X1-X2
n=length(d)
n
dbar=mean(d)
dbar
sd=sqrt(var(d))
sd

#PERFORMING PAIRED t-TEST:
?t.test
#TWO SIDED CASE:
t.test(X1,X2,alternative="two.sided",paired=T,conf.level=0.95)
t.test(d,alternative="two.sided",conf.level=0.95)
#NOTE ABOVE APPROACHES ARE EQUIVALENT

#ONE SIDED CASE UPPER TAIL:
t.test(X1,X2,alternative="greater",paired=T,conf.level=0.95)
t.test(d,alternative="greater",conf.level=0.95)

#ONE SIDED CASE LOWER TAIL:
t.test(X1,X2,alternative="less",paired=T,conf.level=0.95)
t.test(d,alternative="less",conf.level=0.95)