H1 <- seq(0,3,by=.001)         # X axis

   Hcp <- H1*sqrt((20*20)/(20+20))
tcrit2 <- qt(.95,38)
   TII <- pt(tcrit2,38,Hcp)

Pr <- 1-TII                    # Y axis

plot(H1,Pr,type = "l")         # plot