A.27.78 B.1.26 C.1.39 D.1.25
A.對(duì)變量求平均數(shù) B.對(duì)指標(biāo)求平無數(shù) C.對(duì)標(biāo)志求平均數(shù) D.對(duì)標(biāo)志值求平均數(shù)
A.2.63 B.2.25 C.2.73 D.2.2