Ronan, thanks for your points.
We are much earlier -- still in the phase of parameterizing a natural
history discrete events simulation model and calibrating it.
t
On Tue, May 19, 2009 at 4:22 AM, Ronan Conroy <[email protected]> wrote:
> On 18 Beal 2009, at 18:27, Tom Trikalinos wrote:
>
>>>>> To compare non-parametric and parametric survival
>>>>> analysis models, can I use the AIC and BIC?
>>>>> Specifically, I fit Cox PH models and exponential and
>>>>> weibull parametric regressions. It was pointed out to
>>>>> me that AIC & BIC-based comparisons may not be valid
>>>>> (because Cox uses partial likelihood).
>>>>>
>>>>> PS. I am performing survival analyses to inform a decision
>>>>> analysis. For this reason I strongly prefer to fit
>>>>> parametric models - will make life easier and restore the
>>>>> smile on me face.
>
>
> Comparing models for decision making involves assessing the validity and
> utility of the decisions they make. This is not a matter of model fit but of
> defining the characteristics of a desirable model.
>
> For example, if you are developing a model to assess acute chest pain, then
> the critical model errors are false negatives - errors that will result in
> someone with an evolving heart attack being sent home. On the other hand, in
> many screening situations the problem is false positives, who will place a
> burden on diagnostic services.
>
> Ideally, you need to assess your model in a fresh sample. While you can hold
> back some of your estimation sample for validation, this poses the problem
> that factors such as sampling bias, measurement bias etc are common to your
> estimation and validation samples.
>
> I would go for the performance indicators: sensitivity, specificity,
> positive and negative predictive value. Decision makers understand them.
>
> I have seen numerous statistically significant disease predictors that made
> no difference at all the clinical decision making. Indeed, useful predictors
> are far rarer than significant ones.
>
>
>
> Ronan Conroy
> =================================
>
> [email protected]
> Royal College of Surgeons in Ireland
> Epidemiology Department,
> Beaux Lane House, Dublin 2, Ireland
> +353 (0)1 402 2431
> +353 (0)87 799 97 95
> +353 (0)1 402 2764 (Fax - remember them?)
> http://rcsi.academia.edu/RonanConroy
>
> P Before printing, think about the environment
>
>
>
>
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