tmpar <- par( mar=c(4.1,4.1,0,0) )

groups <- 2:20
alpha <- .05

plot( range(groups), c(1,6), type="n",
	xlab="number of groups", ylab="critical value" )
axis(1,c(2,13))
# SCHEFFE
lines( groups, sqrt( qchisq( 1 - alpha, groups - 1 ) ), lty=2 )
text( 13, 5, "SCHEFFE" )
# TUKEY's HSD
lines( groups, c(2.77,3.32,3.63,3.86,4.03,4.17,4.29,4.39,4.47,4.55,4.62,
	4.68,4.74,4.8,4.84,4.89,4.93,4.97,5.01) / sqrt(2), lty=3 )
text( 13, 3, "HSD" )
# BON
comp <- groups * ( groups - 1 )
lines( groups, qnorm( 1 - alpha / comp ) )
text( 13, 3.8, "BONFERRONI" )
# LSD
lines( c(2,20), rep( qnorm( 1 - alpha / 2), 2 ) )
text( 13, 1.6, "LSD" )

rm( alpha, groups, comp )

par( tmpar )