RNGkind("Mersenne-Twister") set.seed(1) V <- rnorm(100,10,2) W <- rnorm(60,12,3) X <- c(V,W) C <- as.factor(c(rep("V",100),rep("W",60))) stripchart(X~C,method="jitter",vert=T,ylim=c(0,20)) MX <- tapply(X,C,mean) SX <- tapply(X,C,sd) IX <- c(1.1,2.1) points(IX,MX,pch=18) arrows(IX,MX-SX,IX,MX+SX,angle=90,code=3) t.test(V,W,var.equal=(var.test(V,W)$p.value>=0.05))