[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: RE: RE: simulate

From   "Nick Cox" <[email protected]>
To   <[email protected]>
Subject   st: RE: RE: simulate
Date   Fri, 4 Sep 2009 16:44:27 +0100

That's helpful. 

[email protected] 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Maarten buis
Sent: 04 September 2009 16:24
To: stata list
Subject: st: RE: simulate

--- Andrzej Niemierko wrote:
> > I am trying to validate my logistic regression model by calculating a
> > distribution of area under the ROC curve for bootstrap samples of my
> > original data.

--- Nick Cox wrote:
> Let's take this step by step: 
> 1. If you want a new ROC area for each new bootstrap sample that you
> draw, you can only do that after the sample is drawn. 
> 2. That must therefore be done within your program, and all under the
> aegis of -simulate-. 
> Thus -mysim- must call -logistic-. 

I think the key word in Andrzej question is "validate". In some areas 
this term means estimate a model in a sample, compute a fit statistic 
of that model in (many) alternative sample, and use these fit statistics
as a measure of fit. If I remember correctly this is supposed to protect
against overfitting or capitalizing on chance: You are trying to look at 
how well the model generalizes to other populations. I (barely) know of 
its existence, so I can't comment on its merrit, but this would seem to 
me to make Andrzej request reasonable (and I gave a sugestion on how to 
do it in an earlier post).

*   For searches and help try:

© Copyright 1996–2024 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index