The problem in #14 is revealed by the line:
Now let's count your predictor variables. You have ib3.Industry11_num, and since we know there are 9 values of Industry11_num, that gives you 8 variables. There is then i.advisor_num--I don't know how many of these there might be, but there's at least one. That brings us to 9. Then from the output table I see two more shown: epsv55 and tsrv411. That makes 11. There may be more that aren't shown, I can't tell. Anyway, with 9 clusters you can't have more than 8 predictor variables and still be able to get an overall model chi square test. So that's the reason the chi square statistic is given as a missing value. You have more than exhausted your available degrees of freedom.
As for whether you should be concerned about it, that depends on your research goals. In most situations, the overall model chi square is irrelevant, and the inability to calculate it is of no importance (the coefficient standard errors and CIs and p-values are all unaffected by this). Only if the overall model chi square is for some unusual reason actually important to answering your research question would this be a matter of concern.
All of that said, 9 clusters is too few to use the cluster robust vce anyway. Its properties are based on asymptotics and require an ample number of clusters for validity. In samples with only a few clusters, as here, it can actually be worse than the ordinary vce. There is no consensus about how many is enough, but I think everyone would agree that 9 is too few.
(Std. Err. adjusted for 9 clusters in Industry11_num)
As for whether you should be concerned about it, that depends on your research goals. In most situations, the overall model chi square is irrelevant, and the inability to calculate it is of no importance (the coefficient standard errors and CIs and p-values are all unaffected by this). Only if the overall model chi square is for some unusual reason actually important to answering your research question would this be a matter of concern.
All of that said, 9 clusters is too few to use the cluster robust vce anyway. Its properties are based on asymptotics and require an ample number of clusters for validity. In samples with only a few clusters, as here, it can actually be worse than the ordinary vce. There is no consensus about how many is enough, but I think everyone would agree that 9 is too few.
Comment