方差是概率论和数理统计中用来度量变量的偏离程度的统计量.由于和方差有关的公式、概念、规律和分析方法比较复杂,有的甚至已经涉及到高等数学的有关的思想,中学生对这部分内容普遍感到难以接受.其实,我们经常遇到的与方差有关的数学问题并不像想象中的那么难,其中,一把对解决问题至关重要的“尚方宝剑”就是方差公式.它有着极其广阔的应用价值.很多题目只要灵活利用方差公式,就能使问题得到巧妙的解决,达到事半功倍的效果. Variance is a measure of the degree of deviations in probability and mathematical statistics used to measure variables, and because of the complexity and complexity of concepts, laws, and analytical methods associated with variance, some have even touched upon the ideas of higher mathematics, This part of the general feeling unacceptable.In fact, we often encounter and variance-related mathematical problems are not as difficult as imagined, of which, to solve the problem is essential, “Shang Fang Bao Jian” is the variance formula It has a very wide application value.Many questions as long as the flexible use of variance formula, can make the problem be cleverly solved, to achieve a multiplier effect.