A diagram suggested by Tukey in 1971, for comparing an observed bar chart or histogram (with equal-width categories) with a theoretical probability distribution. The comparison is made easier by ‘hanging’ the observed results from the theoretical curve, so that the discrepancies are seen by comparison with the horizontal axis rather than a sloping curve. As in the rootogram, the vertical axis is scaled to the square-root of the frequencies so as to draw attention to discrepancies in the tails of the distribution.
Hanging rootogram. The data are the body densities (in gm/cm3) of 200 men. The diagram suggests that a normal distribution provides an acceptable description.
Subjects: Probability and Statistics.