相依回归系统参数的待定系数估计法

A METHOD OF UNDETERMINED COEFFICIENT IN ESTIMATING TWO SEEMINGLY UNRELATED REGRESSION EQUATIONS

  • 摘要: 对于由两个相依回归方程组成的相依回归系统Yi=Xiβi+δii=1,2),本文提出了参数βi的一种含有待定系数的估计方法.例如,β1的估计为\beta_1^*(K)=\left(X_1^\prime X_1\right)- _1 X_1^\prime\left(Y_1-\frac\sigma_12\sigma_22 N_2 Y_2-K \frac\sigma_12^2\sigma_11 \sigma_22 P_2 Y_1\right)其中K是待定常数,与β1*K)对应的非限定两步估计记为β1*K,T).当K=0时,β1*K)等于协方差改进估计\hat\beta_1(见1),当K=1时,β1*K)等于2提出的一种有偏估计\hat\beta_1.结果表明.总可以选取适当的K值.在一定条件下使β1*K)和β1*K,T)分别在均方误差矩阵准则下优于\hat\beta_1和\hat\beta_1(T).本文还讨论了K值的最佳选择问题。

     

    Abstract: For the system of two seemingly unrelated regression equations: Yi=Xiβi+δii=1,2), a new method of estimating βi’s is introduced in this paper. Theestimator of β1 is given as\beta_1^*(K)=\left(X_1^\prime X_1\right)^-1 X_1^\prime Y_1-\frac\sigma_12\sigma_22\left(X_1^\prime X_1\right)^-1 X_1 N_2 Y_2-K \frac\sigma_12^2\sigma_11 \sigma_22\times\left(X_1^\prime X_1\right)^-1 X_1^\prime P_2 Y_1, where K is an arbitrary constant. The unrestricted two-step estimator, which is the feasible counterpart to β1*K), is denoted asβ1*K,T). In particular, β1*(1)=\widetilde\beta_1, the covariance improved estimator introduced in 1, and β1*(1)=\widetilde\beta_1, a biased estimator introduced in 2. It is shown that choosing a reasonable K, the estimator β1*K) may work better than\widetilde\beta_1, and β1*K,T) may perform better than \widetilde\beta_1(T), with respect to the mean square error matrix (MSEM) criterion. How to choose the optimal value of K is also discussed.

     

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