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RE: st: Trouble with estat classification
From
"Dukes, Jonathan" <[email protected]>
To
"[email protected]" <[email protected]>
Subject
RE: st: Trouble with estat classification
Date
Wed, 5 Feb 2014 19:37:39 +0000
I should preface with the fact that I used a dichotomized variable in the roctab (i.e. 0=Maternal Age LT 35, 1=Maternal Age GT 35).
roctab USabnormal matage, summary detail
------------------------------------------------------------------------------
Correctly
Cutpoint Sensitivity Specificity Classified LR+ LR-
------------------------------------------------------------------------------
( >= 0 ) 100.00% 0.00% 30.38% 1.0000
( >= 1 ) 12.50% 80.00% 59.49% 0.6250 1.0938
( > 1 ) 0.00% 100.00% 69.62% 1.0000
------------------------------------------------------------------------------
logistic USabnormal matage
estat classification
-------- True --------
Classified | D ~D | Total
-----------+--------------------------+-----------
+ | 0 0 | 0
- | 24 55 | 79
-----------+--------------------------+-----------
Total | 24 55 | 79
Classified + if predicted Pr(D) >= .5
True D defined as USabnormal != 0
--------------------------------------------------
Sensitivity Pr( +| D) 0.00%
Specificity Pr( -|~D) 100.00%
Positive predictive value Pr( D| +) .%
Negative predictive value Pr(~D| -) 69.62%
--------------------------------------------------
False + rate for true ~D Pr( +|~D) 0.00%
False - rate for true D Pr( -| D) 100.00%
False + rate for classified + Pr(~D| +) .%
False - rate for classified - Pr( D| -) 30.38%
--------------------------------------------------
Correctly classified 69.62%
--------------------------------------------------
Respectfully,
Jonathan
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Richard Goldstein
Sent: Wednesday, February 05, 2014 1:27 PM
To: [email protected]
Subject: Re: st: Trouble with estat classification
there is nothing wrong here - they are just doing different things:
estat classification uses one cutpoint; -roctab- uses more than one as shown in the documentation
Rich
On 2/5/14, 2:17 PM, Dukes, Jonathan wrote:
> Dear Statalist,
>
> I used estat classification after a logistic regression to find the
> sensitivity,
specificity, and positive predictive value. Using estat classification I get a sensitivity of 0% and a specificity of 100%. However, using roctab I get a sensitivity of 12.5% and specificity of 80%. Does anybody have an idea of what is wrong with the estat classification statement? Thank you for your help.
>
>
>
>
> Very Respectfully,
>
> Jonathan
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