再做卫生支出的面板数据分析 staperpop为各省健康工作者,rat65,ratmar为65岁以上人口百分比和结婚率每千人。quietly tesset pre suryea
xtreg exp rat65 ratmar, fe 回归结果中俩解释变量结果
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staperpop | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
rat65 | .6022233 .0303185 19.86 0.000 .5425422 .6619044
ratmar | -.4358449 .2301252 -1.89 0.059 -.88884 .0171503
_cons | 3.599094 1.744338 2.06 0.040 .1654122 7.032775
-------------+----------------------------------------------------------------
sigma_u | 2.9786961
sigma_e | .42635793
rho | .97992348 (fraction of variance due to u_i)
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F test that all u_i=0: F(46, 280) = 313.54 Prob > F = 0.0000
回归方程中加入时间 变量后解释变量的符号彻底反转tesset pre suryea
xtreg exp rat65 ratmar suryea, fe
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staperpop | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
rat65 | -.3830402 .0499103 -7.67 0.000 -.4812889 -.2847916
ratmar | .4824183 .1486509 3.25 0.001 .1897985 .775038
suryea | .5762852 .0270562 21.30 0.000 .523025 .6295454
_cons | 10.4597 1.125417 9.29 0.000 8.244316 12.67509
-------------+----------------------------------------------------------------
sigma_u | 4.4006658
sigma_e | .26357173
rho | .99642558 (fraction of variance due to u_i)
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F test that all u_i=0: F(46, 279) = 830.28 Prob > F = 0.0000
这要如何解释啊。请各位老师指点.