1 Child Health and Development Studies
2 Department of Pediatrics, The Permanente Medical Group, Kaiser Foundation Hospital, Oakland, California
On infant growth curves drawn by the usual technique (Fig. 1, left), it is often difficult to distinguish among the centile lines. The lines for the first few months of life are so steep, and so close together, that a chart must be made inconveniently large to be readable. Plotting the logarithm of the height or weight against age improves distinction only slightly.
A more satisfactory graphic representation of growth data is suggested by the method of Rao.1 A modification of Rao's method, applicable to the longitudinal analysis of growth data, was recently described by one of us (J.W.).2