data(hsgeometry)
dotchart(angles$N.R[, "posttest"], pch = 4,
main = "High school geometry problems",
xlab = "Response frequency (pre- [o] and posttest [x])")
points(angles$N.R[, "pretest"], 1:32)
mtext("Lakshminarayan (1995)", side = 3, line = 0.5)
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