To establish normal growth, a normal growth rate must be demonstrated. To establish the growth rate of a child, height should be measured on two different occasions that are separated by a period of time. The length of time needed to establish a normal growth velocity depends upon the increment that might be expected and the accuracy of the equipment used. Instruments of the type shown in Fig. 14.7 would require approximately three years to establish normality because of the high error margin when using them.
