Dear all,
Not rarely I almost drive myself crazy because several Stata commands fail
to provide info about the formulations they use to compute
variances/standard errors in their calculations.
I have already claimed that most Stata packages should provide references
on their formulae/and or to point out where we can get detailed info on
the methods implemented.
When no reference is given, I usually open the code and see how it was
calculated, trying to find ou in textbooks similar formulations.
However, in the case of the -smrby- command, which calculates the ratio of
OBSERVED/EXPECTED counts and its confidence intervals, I could not figure
out how the global macros S_1 and S_2 were computed.
Once you can rapidly take a look on the code of the -smr- command, I did
not paste the whole code here for simplicity.
Specifically, I am interested in the following lines:
if _rc==0 {
_crccip `o' `level'
local l=100*($S_1/`e')
local u=100*($S_2/`e')
local r=100*(`o'/`e')
local emark ""
}
I will be really grateful for any tip on how both $S_1 and $S_2 were
calculated.
All the best,
Tiago Pereira
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