21.设x1,x2,x3,x 4是来自均值为θ的指数分布总体的样本,其中θ未知,设有估计量-|||-_(1)=dfrac (1)(6)((x)_(1)+(x)_(2))+dfrac (1)(3)((x)_(3)+(x)_(4)),-|||-_(2)=dfrac (({x)_(1)+2(x)_(2)+3(x)_(3)+4(x)_(4))}(5)-|||-_(3)=dfrac (({x)_(1)+(x)_(2)+(x)_(3)+(x)_(4))}(4)-|||-(1)指出T1,T2,T3哪几个是θ的无偏估计量;-|||-(2)在上述θ的无偏估计中指出哪一个较为有效.

12.设X1,X2,X3,X4是来自均值为θ的指数分布总体的样本,其中θ未-|||-知.设有估计量-|||-_(1)=dfrac (1)(6)((X)_(1)+

12.设X1,X2,X3,X4是来自均值为θ的指数分布总体的样本,其中θ未-|||-知.设有估计量-|||-_(1)=dfrac (1)(6)((X)_(1)+

已知 X1,X2,X3 为来自总体 X 的样本, X1,X2,X3 X1,X2,X3 X1,X2,X3, 其中 X1,X2,X3的无偏估计量是 (

[题目]设总体 approx N(mu ,1), (x1,x2,x3)为其样本,-|||-若估计量-|||-mu =dfrac (1)(2)(x)_(1)+df

样本X1,X2,X3来自总体X,若 hat (mu )=dfrac (1)(3)(X)_(1)+-|||-(X)_(2)+dfrac (1)(2)(X)_(3)

设x1,x2,x3为来自正态总体x1,x2,x3的简单随机样本,其中x1,x2,x3为未知参数,下列不是无偏估计的是( )x1,x2,x3设为来自正态总体的简

⑤.边样本x1,x2,x 3是来自总体X,E (X)存在,问 =-|||-时, (X)_(1)+dfrac (2)(5)(X)_(2)+dfrac (1)(6)

4.设总体 sim N(mu ,(sigma )^2), x1,x2,x3为来自X的样本 hat (mu )=dfrac (1)(4)(x)_(1)+b(x)_

设X1,X2为来自正态总体N(μ,σ^2 )的样本,下列不是μ的无偏估计量的是-|||-A (mu )_(1)=dfrac (2)(3)(X)_(1)+dfra

仿样本X1,X2,X是来自总体X,E(X)存在,问 C= ()-|||-时, (X)_(1)+dfrac (2)(5)(X)_(2)+dfrac (1)(6)(