library(ISwR)
data(energy)
energy
attach(energy)


###Normality Test
tapply(expend, stature, shapiro.test)
t.test(expend~stature, var.equal=T)

###Varyans Test
var.test(expend~stature)

###Independent T Test        
t.test(expend~stature, var.equal=T)

###Summary
tapply(expend,stature,mean)
tapply(expend,stature,sd)

xbar<-tapply(expend,stature,mean)
s<-tapply(expend,stature,sd)
n<-tapply(expend,stature,length)
m<-tapply(expend,stature, min)
ma<-tapply(expend,stature, max)
cbind(mean=xbar, std.dev=s, n=n, min=m, max=ma)


###Welch Two Sample t-test

t.test(expend~stature)

### WILCOXON.TEST 

wilcox.test(expend~stature)

###Wilcoxon rank sum test with continuity correction

data:  expend by stature
W = 12, p-value = 0.002122
alternative hypothesis: true location shift is not equal to 0

Warning message:
In wilcox.test.default(x = c(7.53, 7.48, 8.08, 8.09, 10.15, 8.4,  :
  cannot compute exact p-value with ties

######################################################
###PAIRED T TEST
data(intake)
attach(intake)
intake

shapiro.test(intake$pre)
shapiro.test(intake$post)

t.test(pre, post, paired=T)
summary(pre)
summary(post)

###WILCOXON SIGN TEST

wilcox.test(pre, post, paired=T)
 
####ANOVA

data(red.cell.folate)
attach(red.cell.folate)
summary(red.cell.folate)
           
anova(lm(folate~ventilation))
aov(lm(folate~ventilation))
aov(formula = lm(folate ~ ventilation))

###Coefficients
lm(formula = folate ~ ventilation)


###HOMOGENEITY OF VARIANCES(Bartlett test or Levene test ) 

bartlett.test(folate~ventilation)

levene.test(folate~ventilation) ### we need to install package(car)

###POST HOC TEST
pairwise.t.test(red.cell.folate$folate, red.cell.folate$ventilation,
                 p.adjust.method = "bonferroni")
pairwise.t.test(red.cell.folate$folate, red.cell.folate$ventilation,
                 p.adjust.method = "holm")


boxplot(folate ~ ventilation, xlab="ventilation", ylab="folate", las=1,)


###KRUSKAL WALLIS H TEST

kruskal.test(folate~ventilation)

pairwise.wilcox.test(red.cell.folate$folate, red.cell.folate$ventilation,
                 p.adjust.method = "bonferroni")