# Unit 5 for R
# 030521 prepared by C. Andy Tsao
# Concept: Comparing two treatment 
# cf. Chapter 10 of Johnson and Bhattacharyya


x<-c(44,44,56,46,47,38,58,53,49,35,46,30)
y<-c(35,47,55,29,40,39,32,41,42,57,51,39)

# Pre-prelim analysis??? Design and Sampling plan?
# Don't just dump the data into the statware. 
# Reminder: Garbage in, garbage out

# Prelim analysis
stem(x);stem(y);
summary(x);summary(y);
boxplot(x,y)

# Variuos t-tests
t.test(x,y)
t.test(x, y, alternative = c("two.sided"),
       mu = 0, paired = FALSE, var.equal = FALSE,
       conf.level = 0.95)
t.test(x, y, alternative = c("two.sided"),
       mu = 0, paired = FALSE, var.equal = TRUE,
       conf.level = 0.95)
t.test(x, y, alternative = c("two.sided"),
       mu = 0, paired = TRUE, var.equal = TRUE,
       conf.level = 0.90)
       
# Example : on page 425
fwa<-c(44,44,56,46,47,38,58,53,49,35,46,30,41)
dwa<-c(35,47,55,29,40,39,32,41,42,57,51,39)
summary(fwa);summary(dwa);
boxplot(fwa,dwa)
t.test(fwa,dwa, var.equal = TRUE)

# clear up
rm(list=ls(all=TRUE))

# 10.31 on page 438 using R
c1<-c(5,2,8,3);c2<-c(8,9,6);
t.test(c1,c2)
t.test(c1,c2,var.equal=TRUE)

# 10.48 on page 452 (also Example 12 on page 445)
# Switch working dir to where data C10T2.dat is located
t<-matrix(scan("C10T2.dat"),ncol=2,byrow=T)
t
x<-t[,1];y<-t[,2];
x
y
d<-x-y
t.test(d)
t.test(x,y,pair=TRUE)
t.test(x,y)