groups <- 2:10

curve(1-(0.95^(x-1)), 2, 10,
      ylim = c(0,1),
      yaxt="n",
      xlab = "Number of groups",
      ylab = "Type I error"
      )
## Customizing the y-axis
axis(2, at=c(0,0.05,0.5,1),
     labels = c("0",".05", ".5", "1"),
     las=2)

points(groups, 1-0.95^(groups-1),
       pch = 1)

curve(1-(0.95^(x*(x-1)/2)),
      2, 10,
      add=TRUE)

points(groups, 1-(0.95^(groups*(groups-1)/2)),
       pch = 4)