设样本是x1,x2,...,xn则平均数p=(x1+x2+..+xn)/n方差s=(x1-p)^2+(x2-p)^2+...+(xn-p)^2s=0,且(x1-p)^2≥0,(x2-p)^2≥0,...,(xn-p)^2≥0则(x1-p)^2=0,(x2-p)^2=0,...,(xn-p)^2=0则x1=x2=..=xn=p则样本数据相等...