想请教一下大神，对于这个模型我有两点不是很清楚：
1）这里的ui指的是全部的sample的residual, 所以我也是predict e, xb就能得出ui吗？
2）ei指的是上面的这个residual的标准差，那我该怎么去计算这个数值呢？

要是做不出这个我的论文就写不下去了，救救娃吧。


where BTi,t is book-tax gap for firm i in year t, scaled by the lagged value of assets; TAi,t is total accruals for firm i in year t, scaled by the lagged value of assets; ui is the average value of the residual for firm i over the sample period 1993–2001; and ei,t is the deviation inu year t froum firm i’s average residual ui.