设X1,X2,......,Xn平均数为m即 （X1+X2+X3.+XN)/N=M则 aX1+b,aX2+b,......,aXn+b平均数为(aX1+b+aX2+b,......+aXn+b)/n=a(x1+x2.+xn)+nb/n=am+b设X1,X2,......,Xn为S则S=(X1-M)^2+(X2-M)^2.+(XN-M)^2/NaX1+b,aX2+b,....