Question

計(jì)算下面這組數(shù)據(jù)的方差和標(biāo)準(zhǔn)差(結(jié)果精確到0.1):

423,421,419,420,421,417,422,419,423,418.

Answer 1

思路分析：方差、標(biāo)準(zhǔn)差有多種計(jì)算方法,計(jì)算時(shí)要靈活運(yùn)用,以便減輕運(yùn)算量.

解:方法一:s²=［423²+421²+419²+…+423²+418²-10×()²］

=［1 766 559-10×()²］

=［1 766 559-1 766 520.9］

=×38.1≈3.8.

∴s=≈1.9.

方法二:令a=420,將每一個(gè)數(shù)據(jù)都減去a,得到一組新數(shù)據(jù)如下:

3,1,-1,0,1,-3,2,-1,3,-2.

∴s²=［(3²+1²+…+2²)-10×()²］

=［39-10×()²］

=(39-0.9)≈3.8.

∴s=3.8≈1.9.