例:测定铁矿石中铁的质量分数(以表示),5次结果分别为:6748% 67.37%,,6747%,6743%和67.40% 计算:(1)平均偏差(2)相对平均偏差(3)标准偏差;(4)相对标准偏差; (5)极差 6748%+67.37%+6747%+6743%+67407% x =6743% h<1d:005%+0.06%+0.04%+0.03% 0.04% 5 0.049 ×100%= ×100%=0.06 6743 (0.05%)2+(0.06%)2+(0.049%0)2+(0.03%) =005% n Sn=-×10070.05% 100%=0.07% 6743% Xmx大-X小=67.48%-67.37%=0.11%11 例：测定铁矿石中铁的质量分数（以表示），5次结果分别为：67.48% 67.37%，，67.47%，67.43%和67.40%。 计算：（1）平均偏差（2）相对平均偏差 （3）标准偏差;（4）相对标准偏差; （5）极差。 67.43% 5 67.48% 67.37% 67.47% 67.43% 67.407% = + + + + = − x  = + + + = = − 0.04% 5 0.05% 0.06% 0.04% 0.03% | | 1 di n d 100% 0.06% 67.43% 0.04% = 100% =  = − − x d dr 0.05% 5 1 (0.05%) (0.06%) (0.04%) (0.03%) 1 2 2 2 2 2 = − + + + = − =  n d S i 100% 0.07% 67.43% 0.05% = 100% =  = − x S Sr Xm=X大-X小=67.48%-67.37%=0.11%