Dear all,
I have a question related to the missing p-values. my regression function is xtreg yit (performance measures) CDOijt controlsit i.year, fe. However, the problem came when I used the loop command (displayed as follows) to obtain the coefficients of each CDO fixed effect, the p-value of some coefficients was missing. There will be more missing value if I cluster by company.

any suggestions on this issue will be highly appreciated!
I have a question related to the missing p-values. my regression function is xtreg yit (performance measures) CDOijt controlsit i.year, fe. However, the problem came when I used the loop command (displayed as follows) to obtain the coefficients of each CDO fixed effect, the p-value of some coefficients was missing. There will be more missing value if I cluster by company.
Code:
encode Company_id,gen(company)
gen lnassets = log(Totalassets)
xtset company Year
tempname memhold
postfile `memhold' cdo_id CDO_b CDO_pvalue using "result2_post.dta", replace
levelsof CDO_id, local(levels)
foreach x of local levels {
quietly xtreg ROA CDO CF Leverage Investment Cashholdings lnassets i.Year if CDO_id == `x', fe
matrix CDO_coef = e(b)
matrix CDO_se = e(V)
scalar CDO_b = CDO_coef[1, "CDO"]
scalar CDO_se = sqrt(CDO_se[1, 1])
scalar CDO_pvalue = 2 * (ttail(e(df_r), abs(CDO_b / CDO_se)))
post `memhold' (`x') (CDO_b) (CDO_pvalue)
}
postclose `memhold'
use result2_post.dta, clear
list
any suggestions on this issue will be highly appreciated!

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