学习了方差公式,有些学生往往只局限于具体的数字计算之中,没有体会其中的奥妙,实际上方差公式在数学解题中有着广泛的应用.大家知道,如果一组数据x1,x2,x3,…,x n,其平均数为x=1n(x1+x2+x3+…+x n).1方差为S2=1n[(x1-x)2+(x2-x)2+(x3-x)2+…+(x n-x)2].2此方差公式可简化为S2=1n[x21+x22+x23+…+x2n)-nx2].31代入3得S2=1n[x21+x22+x23+…+x2n)- Learn the formula of variance, some students are often confined to the specific numerical calculations, did not understand the mystery, in fact, the variance formula has a wide range of applications in the mathematical problem solving.We all know that if a set of data x1, x2, x3 , ..., xn, the average of which is x = 1n (x1 + x2 + x3 + ... + xn) .1 The variance is S2 = 1n [(x1-x) 2+ (x2-x) 2+ (x3-x) 2 + ... + (x nx) 2] .2 This variance formula simplifies to S2 = 1n [x21 + x22 + x23 + ... + x2n] -nx2] .31 Substituting in 3 gives S2 = 1n [x21 + x22 + x23 + ... + x2n ) -