Re: [R] exact values for p-values - more information.

From: Adaikalavan Ramasamy <ramasamy_at_cancer.org.uk>
Date: Tue 12 Jul 2005 - 03:57:09 EST

Compare the following

   t.test( 1:100, 101:200 )$p.value
   t.test( 1:100, 101:200 )

In the latter, the print method truncates to 2.2e-16. You can go as far as (depending on your machine)

   .Machine$double.xmin
   [1] 2.225074e-308

before it becomes indistinguishable from zero.

But there are good reasons to truncate it at 2.2e-16 such as the difficulty in trying to accurately estimate the extreme tail probabilities.

Regards, Adai

On Mon, 2005-07-11 at 18:52 +0200, S.O. Nyangoma wrote:
> Hi there,
> If I do an lm, I get p-vlues as
>
> p-value: < 2.2e-16
>
> This is obtained from F =39540 with df1 = 1, df2 = 7025.
>
> Suppose am interested in exact value such as
>
> p-value = 1.6e-16 (note = and not <)
>
> How do I go about it?
>
> stephen
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Jul 12 04:08:49 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:33:30 EST