Following is a response from DHS Research & Data Analysis Director, Tom Pullum:
The problem is that when you merged the FW and IR files, (and the FW and MR files) you should have dropped the interviewers who did not match with a woman in the IR file (or a man in the MR file). The following Stata code will work for the FW and IR merge with BU7:
use "C:\Users\26216\ICF\Analysis - Shared Resources\Data\DHSdata\BUFW71FL.DTA", clear
keep fw101 fw105
rename fw101 interviewer_id
rename fw105 interviewer_sex
sort interviewer_id
save tempfw.dta, replace
use "C:\Users\26216\ICF\Analysis - Shared Resources\Data\DHSdata\BUIR71FL.DTA", clear
keep v028
rename v028 interviewer_id
sort interviewer_id
merge interviewer_id using tempfw.dta
tab _merge interviewer_sex
keep if _merge==3
tab interviewer_sex
I use an older version of the merge command, but whatever version you use, you need to drop the cases for which _merge is not 3.
Good to see that you are using the FW files!