各位大神,麻烦帮忙看看,用stata做面板数据回归的时候,hausman检验的结果是chi2(1)=-0.00,p值没有,这是怎么回事啊?谢谢大家了!
. xtreg car lntv aer cr4,fe
Fixed-effects (within) regression Number of obs = 143
Group variable: code Number of groups = 13
R-sq: Obs per group:
within = 0.0669 min = 11
between = . avg = 11.0
overall = 0.0141 max = 11
F(3,127) = 3.04
corr(u_i, Xb) = -0.0000 Prob > F = 0.0316
------------------------------------------------------------------------------
car | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
lntv | -.0547635 .8400366 -0.07 0.948 -1.717044 1.607517
aer | -5.832483 18.51818 -0.31 0.753 -42.47663 30.81166
cr4 | 2.207262 5.925258 0.37 0.710 -9.517753 13.93228
_cons | 12.0607 6.56496 1.84 0.069 -.9301739 25.05157
-------------+----------------------------------------------------------------
sigma_u | 1.1336242
sigma_e | .57679278
rho | .79435579 (fraction of variance due to u_i)
------------------------------------------------------------------------------
F test that all u_i=0: F(12, 127) = 42.49 Prob > F = 0.0000
. estimates store FE
. xtreg car lntv aer cr4,re
Random-effects GLS regression Number of obs = 143
Group variable: code Number of groups = 13
R-sq: Obs per group:
within = 0.0000 min = 11
between = 0.0000 avg = 11.0
overall = 0.0141 max = 11
Wald chi2(3) = 9.11
corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0278
------------------------------------------------------------------------------
car | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
lntv | -.0547635 .8400366 -0.07 0.948 -1.701205 1.591678
aer | -5.832483 18.51818 -0.31 0.753 -42.12746 30.46249
cr4 | 2.207262 5.925258 0.37 0.710 -9.406029 13.82055
_cons | 12.0607 6.572307 1.84 0.066 -.820789 24.94218
-------------+----------------------------------------------------------------
sigma_u | 1.120205
sigma_e | .57679278
rho | .79043804 (fraction of variance due to u_i)
------------------------------------------------------------------------------
. estimates store RE
. hausman FE RE,constant sigmamore
Note: the rank of the differenced variance matrix (1) does not equal the number of coefficients being
tested (4); be sure this is what you expect, or there may be problems computing the test. Examine
the output of your estimators for anything unexpected and possibly consider scaling your variables
so that the coefficients are on a similar scale.
---- Coefficients ----
| (b) (B) (b-B) sqrt(diag(V_b-V_B))
| FE RE Difference S.E.
-------------+----------------------------------------------------------------
lntv | -.0547635 -.0547635 -9.72e-13 8.11e-07
aer | -5.832483 -5.832483 -2.24e-11 .0000183
cr4 | 2.207262 2.207262 3.56e-12 3.11e-06
_cons | 12.0607 12.0607 7.64e-12 .
------------------------------------------------------------------------------
b = consistent under Ho and Ha; obtained from xtreg
B = inconsistent under Ha, efficient under Ho; obtained from xtreg
Test: Ho: difference in coefficients not systematic
chi2(1) = (b-B)'[(V_b-V_B)^(-1)](b-B)
= -0.00 chi2<0 ==> model fitted on these
data fails to meet the asymptotic
assumptions of the Hausman test;
see suest for a generalized test
.


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