Re: st: Wald interval and the WSJ

[David Airey <david.airey@Vanderbilt.Edu>]

.

Another point of view is that for something like a stent that goes in  
a human body, I'd want my probability to be quite a bit better than . 
05 anyway, like .01 or .001. I've seen a lot of .05 results evaporate  
on additional scrutiny. And also the article doesn't emphasize effect  
size, which might make the quibbling over p values moot too.

-Dave

On Aug 14, 2008, at 8:56 AM, Maarten buis wrote:


> It looks to me (though the article doesn't say) that this deals with a
> test of multinomial proportions. This is a difficult problem, the  
> exact
> test statistic exists, but is actually not exact at all but
> conservative, various other/better approximations have been proposed,
> but now you have to decide how to choose between them. In this case  
> all
> the different p-values are very close to .05 (from .049 to .052  
> whith a
> spike at .55) The articles puts great emphasis on the fact that all  
> but
> one test results in p-values more then .05, and that the company
> conveniently choose the one test that supported their claim. That may
> or may not be suspicious, but my reading of a study like this is that
> these numbers are so close to .05 (and there is nothing magical or
> `scientific' about the number .05) that making a big deal about a  
> black
> and white distinction between significant and non-significant is  
> pretty
> ridiculous. I know that this doesn't help an agency like the FDA who
> have to make a approve or disaprove decision (and they certainly don't
> ask my advise), but sometimes a study just ends up in a grey area
> between significant and insignificant.
>
> -- Maarten
>
> --- Scott Merryman <scott.merryman@gmail.com> wrote:
>
>
> > There is an interesting article in today's Wall Street Journal on the
> > use of the Wald interval in clinical trials.
> >
> > "Boston Scientific Stent Study Flawed"  by Keith Winstein, August 14,
> > 2008; Page B1.
> >
> > "But Boston Scientific's claim was based on a flawed statistical
> > equation that favored the Liberte stent, a Journal analysis has
> > found.
> > Using a number of other methods of calculation -- including 14
> > available in off-the-shelf software programs -- the Liberte study
> > would have been a failure by the common standards of statistical
> > significance in research.
> > Boston Scientific isn't the only company to use the equation, known
> > as
> > a Wald interval, which has long been criticized by statisticians for
> > exaggerating the certainty of research results. "
> http://digg.com/business_finance/WSJ_com_Boston_Scientific_Stent_Study_Flawed
> > Scott
> > *
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>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
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> 1081 HV Amsterdam
> The Netherlands
>
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>
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>
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