人民教育出版社初中代数第三册教师教学用书第 171页有一段话 :“在讲方差概念时 ,有的同学会提出疑问 :为什么要这样定义方差 ?在表示各数据与其平均数的偏离程度时 ,为了防止偏差和负偏差的相互抵消 ,为什么对各数据与其平均数的差不取其绝对值 ,而要将它们平方 ?实际上 ,这 People’s Education Press Junior Middle School Algebra The third volume of the teacher’s teaching book is on page 171. There is a paragraph: “When you talk about the concept of variance, some students ask questions: Why do you want to define the variance? When you indicate the deviation of each data from its average number, In order to prevent deviations and negative deviations from cancelling each other out, why does the difference between each data and its average number not take its absolute value, but square it? In fact, this