Normalizing transformations for growth standards

Age-specific distributions of growth measurements, either distances or velocities, can be normalized in various ways. This paper studies the polynomial method of Healy, Rasbash and Yang (1988), Cole's (1988) power transformation and the logarithmic transformation with adjustable start. The methods are used to fit the centiles for boys' weight and for boys' height velocity from Tanner, Whitehouse and Takaishi (1966). The power and logarithmic transformations behave very similarly; the polynomial method gives less satisfactory results. The first two methods differ, however, at extreme low centiles for weight, and both give rise to problems with height velocity near adulthood.