D-I-D 后得到如下结果:
为何第二期被解释变量的均值为负? 而我的样本中,tfe均为正值。怎么可能会出现负的平均值?其表明什么问题?
Outcome Variable | Control | Treated | Diff(BL) | Control | Treated Diff(FU) | DIFF-IN-DIFF |
| | | | | | |
fte | 0.018 | 0.434 | 0.415 | -0.781 | -0.303 0.478 | 0.062 |
Std. Error | 2.399 | 2.39 | 0.296 | 2.405 | 2.402 0.298 | 0.398 |
t | 0.01 | 0.19 | 1.4 | -0.31 | -0.34 0.62 | 0.16 |
P>t | 0.994 | 0.856 | 0.162 | 0.746 | 0.900 0.110 | 0.875 |