. xtreg Cscore Overconf Own Salesgrowth Invest CFO Revenue ROA B1-B3 Indcd1-Indcd17,fe r
note: B3 omitted because of collinearity
note: Indcd12 omitted because of collinearity
note: Indcd15 omitted because of collinearity
Fixed-effects (within) regression Number of obs = 4110
Group variable: Stkcd Number of groups = 1370
R-sq: within = 0.3393 Obs per group: min = 3
between = 0.0910 avg = 3.0
overall = 0.1341 max = 3
F(23,1369) = .
corr(u_i, Xb) = 0.0147 Prob > F = .
(Std. Err. adjusted for 1370 clusters in Stkcd)
在做面板数据回归的时候我用了固定效应模型,同时加入了年度和行业虚拟变量,stata显示的回归结果如上。我想问一下,我的命令应该是对的吧,可是回归出来F统计量和P值都没有数是什么原因啊?