波动率volability其实在经济学里面多指的是方差variance(σ^2)

x^2=31.575平均值, ∑(x-x^)^2/(n-1)=[（34-31.575)^2+(35-31.575)^2+(31.2-31.575)^2+(26.1-31.575)^2]/(4-1)=19.2709/3=6.42