### LESSON 4 EXERCISES OF T TEST & WILCOXON Rank TEST  (19/4/2021)

library(haven)
setwd("S:/_STAFF/Gulser/R NOTES/LESSON_4")
dataset<-read_dta('all707387.dta')
attach(dataset)
dataset
summary(dataset)


detach(dataset)
dataset$drug<-factor(dataset$drug, labels=c("diuretico", "beta-bloccante "))
attach(dataset)
summary(dataset)

tapply(FreqCard , drug, shapiro.test)

###Varyans Test
var.test(FreqCard~drug)

###Independent T Test        
t.test(FreqCard~drug, var.equal=T)

###Summary
tapply(FreqCard,drug,mean)
tapply(FreqCard,drug,sd)

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


###Welch Two Sample t-test(if varyans)

t.test(FreqCard~drug)

### WILCOX.TEST 

wilcox.test(FreqCard~drug)