(2)简单随机抽样比估计 a=yx=Rx=1.101236×826800=910502(亩) s(n)≈4,/(1-f) (S2+R322R)=23095(亩 (3)分层随机抽样 单估计 ∑NDn=910780(亩) s(x)=N√w(Jx)=N ∑W hh nN h=1 =976 23976 )(0.4375×42064.933+0.3043×3122.71+0.2582×121470.667) 48975(亩)(2)简单随机抽样比估计 ˆ 1.101236 826800 910502( ) R y y X RX x = = =  = 亩 2 2 2 (1 ) ˆ ( ) ( R y x f s y N S R S n −  + ˆ 2 ) 23095( ) − = RSxy 亩 (3)分层随机抽样简单估计 1 910780( ) k st h h h y N y = = =  亩 ( ) ( ) st st s y N v y = 2 1 1 1 ( ) k h h h N W S n N = = −  1 1 976 ( )(0.4375 42064.933 0.3043 31221.571 0.2582 121470.667) 23 976 = −  +  +  = 48975(亩）