proportionality coefficient

例句：

1. 1. The proportion of students who failedthe exam was 20%.
   考试不及格的学生占20%。
2. 2. The ratioof male to female students in this classis 3:2.
   这个班级男生和女生的比例是3:2。
3. 3. Thecoefficient of variation measures how much the datavaries from its mean value.
   变异系数衡量数据与均值的偏离程度。