function (n = 6, m = 4,  PDF = F) 
{
    if (PDF == T) 
        pdf(file = paste("contcorrnCDF", n, "m", m, ".pdf", 
            sep = ""), width = 11)
    N = m + n
    mean.WXY = n * (N + 1)/2 - n * (n + 1)/2
    var.WXY = m * n * (N + 1)/12
    x = 0:(m * n)
    
    probs = pwilcox(x, n, m)
    out=stepfun(x,c(0,probs))
    plot.stepfun(out,xlab="a",ylab=expression(F(x)==P(W[XY]<=a)),pch=16,cex=.7,xlim=c(-5,m*n+5),
    main="",axes=F)
axis(1)
axis(2)
abline(h=c(0,1))
z=seq(-5,m*n+5,length.out=200)
pz=pnorm(z,mean.WXY,sqrt(var.WXY))
lines(z,pz,col="blue")
px=pnorm(x,mean.WXY,sqrt(var.WXY))
px1=pnorm(x+.5,mean.WXY,sqrt(var.WXY))
points(x,px,pch=16,cex=.7,col="red")  
points(x+.5,px1,pch=16,cex=.7,col="green")    
text(-4,.95,"Normal Approximation to CDF",adj=0)
legend(-5,.9,c("true CDF","without continuity correction","with continuity correction"),
      pch=c(16,16,16),col=c("black","red","green"),bty="n")
text(m*n+5,.9,paste("n =",n," ,  m =",m),adj=1)
    if (PDF == T) 
        dev.off()
}