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Re: st: AW: graphing sensitivity and specificity for a binary test outcome


From   Michael McCulloch <mm@pinest.org>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: AW: graphing sensitivity and specificity for a binary test outcome
Date   Tue, 10 Nov 2009 08:50:04 -0800

Thanks Martin, -roctab- doesn't seem suitable for this purpose because  
my simulated test is only binary, without cut-points.
However, I have tested -senspec-, and am puzzled by the output. 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-?
Michael

***
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)
* A ntneg sp  	B nfneg fneg  	C nfpos fpos  	D ntpos se
list test disease ntneg spec nfneg fneg nfpos fpos ntpos sens in 1/10
***


On Nov 10, 2009, at 12:22 AM, Martin Weiss wrote:

>
> <>
>
> Have you had a look at -roctab- and friends? Also see -ssc d  
> senspec- by
> Roger Newson...
>
>
>
> HTH
> Martin
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Michael
> McCulloch
> Gesendet: Dienstag, 10. November 2009 07:04
> An: Statalist Statalist
> Betreff: st: graphing sensitivity and specificity for a binary test  
> outcome
>
> Dear Statalist members,
>
> With the following code I simulate diagnostic data and, in the last
> line, estimate specificity (cell A in the 2x2 table) and sensitivity
> (cell D).
> What I'm hoping to learn is how to create a bar graph that would
> display the specificity and sensitivity percentages for both methods 1
> and 2.
>
> ***
> 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
> list in 1/20
> tab test disease, row
> gen device=1 + int(2*uniform())	
> bysort device: tab test disease, row
> ***
>
>
>
>
> 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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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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