levels<-levels(data3$x)
group1<-subset(data3,data3$x==levels[1])
group2<-subset(data3,data3$x==levels[2])
boxplot(group1$y,group2$y, names=levels, ylab=ytext)
t_test<-t.test(group1$y, group2$y, var.equal=TRUE)
t_test