It is the difference between the upper and lower quartiles.
2
上四分位数是25%的观察值位于其上的值。
The upper quartile is that value above which 25 per cent of the observations lie.
3
统计中已有确定中位数、四分位数、十分位数等的方法,文章在此基础上提出三分位数的概念及其确定的方法。
There already exist Median, Quartiles and Tenth quantile etc. Based on this, the authors put out the concept and (calculation) method for tri-sectional quantiles in this article.