[R] P values

Bert Gunter gunter.berton at gene.com
Tue May 11 23:50:29 CEST 2010

Inline below.

-- Bert 

Bert Gunter
Genentech Nonclinical Statistics

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Greg Snow
Sent: Tuesday, May 11, 2010 2:37 PM
To: Bak Kuss; murdoch.duncan at gmail.com; jorismeys at gmail.com
Cc: R-help at r-project.org
Subject: Re: [R] P values



"  Small p-values indicate a hypothesis and data that are not very
consistent and for small enough p-values we would rather disbelieve the
hypothesis (though it may still be theoretically possible). "

This is false. 

It is only true when the hypotheses are prespecified (not derived from
looking at the data first), when there's only one being tested (not,say,
10,000), etc. etc. 

(Incidentally, "small enough" is not meaningful; making it so is usually

IMHO far from being niggling details, these are the crux of the reason that
the conventional use of P values to decide what is scientifically "valid"
and what is not is a pox upon science. This is not an original view, of

Don't want to stir up a hornet's nest, so feel free to silently dismiss. But
contrary views are welcome, as always.

No more from me on this -- I promise!

-- Bert

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