In this paper, authors advised a new method calculating the cumulative relative frequency, to study frequent distribution of plant size in the population. To investigate the distribution and frequency of symptoms in manic - depressive disorder. 提出了在解析植物群体的直径分布时不划分直经阶,直接求累计频度的方法;目的调查住院躁狂和抑郁症的症状分布和频度。