A Comparative Study on Three Methods for Working Out the Maximum Increment Age: Based on the data of the Harpenden Growth Study

By making use of the data of the Harpenden Growth Study with a high degree of measurement accuracy, the maximum increment age (MIA) was calculated by three methods; i. e., the proportional allotment method (PA method), the graphical fitting method (GF method), and the theoretical function fitting method (FF method). The MIAs gained by these three methods were analyzed based on the regression line which went through the origin of the coordinate axes. The results were as follows; 1) The slope of the regression line of MIA by the PA method on MIA by the GF method was 0.9972 and the coefficient of determination was 0.9640. The MIAs by both methods agreed well with each other. 2) The slope of the regression line of MIA by the PA method on MIA by the FF method was 1.0032 and the coefficient of determination was 0.9831. They also showed a considerable agreement with each other. 3) MIA by the PA method agreed with MIA by the GF method no less than MIA by the FF method. 4) MIA by the PA method did not change very much even if annual physical examinations were carried out at various times of the year. 5) Finally, it was made clear that these findings proved the PA method to be convenient as a calculation procedure for working out MIA and suitable for analyzing the acceleration of growth. It is concluded that the PA method is no less accurate in computing MIA than the other two methods.