求助:豪斯曼检验最后出来的结果好像有问题(下文蓝色字体处),有大佬知道是怎么回事吗?
xtreg trade GDPi GDPj popi popj disij,re
note: popj omitted because of collinearity
Random-effects GLS regression Number of obs = 100
Group variable: id Number of groups = 10
R-sq: Obs per group:
within = 0.2190 min = 10
between = 0.6558 avg = 10.0
overall = 0.4570 max = 10
Wald chi2(4) = 38.95
corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000
trade Coef. Std. Err. z P>z [95% Conf. Interval]
GDPi .0000631 .0000551 1.15 0.252 -.0000448 .0001711
GDPj .0016759 .0005269 3.18 0.001 .0006433 .0027085
popi 1.295806 7.335467 0.18 0.860 -13.08144 15.67306
popj 0 (omitted)
disij -740663.6 183174.4 -4.04 0.000 -1099679 -381648.3
_cons 1714168 9.58e+09 0.00 1.000 -1.88e+10 1.88e+10
sigma_u 3.657e+08
sigma_e 5.140e+08
rho .33611913 (fraction of variance due to u_i)
. est store re
. xtreg trade GDPi GDPj popi popj disij,fe
note: popj omitted because of collinearity
note: disij omitted because of collinearity
Fixed-effects (within) regression Number of obs = 100
Group variable: id Number of groups = 10
R-sq: Obs per group:
within = 0.2244 min = 10
between = 0.0127 avg = 10.0
overall = 0.0306 max = 10
F(3,87) = 8.39
corr(u_i, Xb) = -0.7497 Prob > F = 0.0001
trade Coef. Std. Err. t P>t [95% Conf. Interval]
GDPi .0000522 .0000565 0.92 0.358 -.00006 .0001645
GDPj .0029001 .0015381 1.89 0.063 -.0001571 .0059572
popi .9297718 7.33495 0.13 0.899 -13.64924 15.50878
popj 0 (omitted)
disij 0 (omitted)
_cons -2.35e+09 9.54e+09 0.25 0.806 -2.13e+10 1.66e+10
sigma_u 1.012e+09
sigma_e 5.140e+08
rho .7947816 (fraction of variance due to u_i)
F test that all u_i=0: F(9, 87) = 15.14 Prob > F = 0.0000
est store fe
hausman re fe,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))
re fe Difference S.E.
GDPi .0000631 .0000522 .0000109 .
GDPj .0016759 .0029001 -.0012242 .
popi 1.295806 .9297718 .3660337 .
_cons 1714168 -2.35e+09 2.36e+09 6.45e+08
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)
= 13.34
Prob>chi2 = 0.0003
(V_b-V_B is not positive definite)


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