求教各位大侠:
我在用eviews 6.0做一个Y=c+dum1+dum2+....+dum15+X1+X2的方程估计之后用white检验,结果显示存在异方差。
在用Glejser检验时,在regressor一栏中默认把虚拟变量都填上了,这样有必要吗?
我的处理办法是:
用Glejser法时,只填了X1,X2,结果发现X1和残差绝对值存在显著关系。
Heteroskedasticity Test: Glejser
F-statistic 15.94163 Prob. F(2,290) 0.0000
Obs*R-squared 29.02230 Prob. Chi-Square(2) 0.0000
Scaled explained SS 35.80900 Prob. Chi-Square(2) 0.0000
Test Equation:
Dependent Variable: ARESID
Method: Least Squares
Date: 09/19/10 Time: 20:48
Sample: 1 308
Included observations: 293
Coefficient Std. Error t-Statistic Prob.
C 0.360870 0.021665 16.65691 0.0000
RETAILBASEYEAR -0.045869 0.008954 -5.122590 0.0000
INTERACTION -0.000945 0.006931 -0.136334 0.8917
R-squared 0.099052 Mean dependent var 0.281432
Adjusted R-squared 0.092839 S.D. dependent var 0.289431
S.E. of regression 0.275669 Akaike info criterion 0.270955
Sum squared resid 22.03809 Schwarz criterion 0.308636
Log likelihood -36.69486 Hannan-Quinn criter. 0.286046
F-statistic 15.94163 Durbin-Watson stat 1.440005
Prob(F-statistic) 0.000000
然后用1/X1作为权重进行WLS估计,得到新的结果。
再用Glejser法,只填了X1、X2,结果是:
Heteroskedasticity Test: Glejser
F-statistic 0.317522 Prob. F(1,291) 0.5735
Obs*R-squared 0.319356 Prob. Chi-Square(1) 0.5720
Scaled explained SS 0.569121 Prob. Chi-Square(1) 0.4506
Test Equation:
Dependent Variable: AWRESID
Method: Least Squares
Date: 09/19/10 Time: 20:50
Sample: 1 308
Included observations: 293
Collinear test regressors dropped from specification
Coefficient Std. Error t-Statistic Prob.
C 0.527623 0.052326 10.08341 0.0000
INTERACTION*WGT -0.003528 0.006261 -0.563491 0.5735
R-squared 0.001090 Mean dependent var 0.524196
Adjusted R-squared -0.002343 S.D. dependent var 0.888562
S.E. of regression 0.889603 Akaike info criterion 2.610719
Sum squared resid 230.2953 Schwarz criterion 2.635839
Log likelihood -380.4703 Hannan-Quinn criter. 2.620780
F-statistic 0.317522 Durbin-Watson stat 1.267130
Prob(F-statistic) 0.573534
这样是否说明已经消除异方差性?(加权之后无法用white检验了,提示观测值不够……)