husman检验后用随机效应模型，可是输出计量结果时，各个截面random effects都为0，怎么回事？[img]file:///C:/Documents%20and%20Settings/Administrator/Application%20Data/Tencent/Users/345828810/QQ/WinTemp/RichOle/4O%7DB5%602U%60%60S%7B%252M])[%7DI%7DHR.jpg[/img]