The coefficient of variation 1. 1 is the variation index expressed in the form of relative number. It is obtained by comparing the full range, average difference or standard deviation in the variation index with the average value. The standard deviation coefficient is commonly used. The application conditions of coefficient of variation 1.2 are as follows: when the levels of two comparison series are different, full scale, average difference or standard deviation cannot be used for comparative analysis, because they are all absolute indicators, and their values are not only affected by the differences of each unit mark value; In order to compare and analyze the variation degree of marker values between variable sequences with different levels, it is necessary to eliminate the influence of levels and then calculate the coefficient of variation.