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st: -senspec- interpretation question


From   Michael McCulloch <mcculloch@pinestreetfoundation.org>
To   Statalist Statalist <statalist@hsphsun2.harvard.edu>
Subject   st: -senspec- interpretation question
Date   Tue, 10 Nov 2009 12:45:38 -0800

Dear Statalist folks,
I'd like to ask advice on interpreting the output of -senspec-. I've created the following simple simulation example which allows me to compare the -senspec- output to a simple 2x2 table. The following code shows that the absolute numbers from -senspec- agrees with each cell of my 2x2 table, but the frequency values are different. Am I misinterpreting or mis-applying -senspec-?

clear
set obs 1000
set seed 12358	
gen test=1 + int(2*uniform())	
replace test=0 if test==2
replace test=1 in 1/300		
gen disease=0 in 1/500
replace disease=1 in 501/1000
tab test disease, row
gen method=1 + int(2*uniform())	
bysort method: tab test disease, row
tab test disease if method==1, row
senspec disease test if method==1, se(sens) spe(spec) fpos(fpos) ntneg(ntneg) fneg(fneg) ntpos(ntpos) nfpos(nfpos) nfneg(nfneg) * cellA: ntneg sp cellB: nfneg fneg cellC: nfpos fpos cellD: ntpos se
list test disease ntneg spec nfneg fneg nfpos fpos ntpos sens in 1/10



Thank you kindly.



Michael McCulloch
Pine Street Foundation
124 Pine Street
San Anselmo, CA 94960-2674
tel:	415-407-1357
fax: 	206-338-2391
mm@pinestreetfoundation.org






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