1009 =0.14/15.82×100%=0.89% x,-x 0.152+0.132+0.212+0.072 S= i=1 =0.17 n-1 3 S 0.17 RSD- ×100%=1.1% X ×100%= 15.82 = 100% X d Rd =0.14/15.82×100%=0.89% =0.17 ( ) 3 0.15 0.13 0.21 0.07 1 2 2 2 2 1 2 + + + = − − = = n X X S n i i 100% 1.1% 15.82 0.17 = 100% =  = X S RSD