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

[Adaikalavan Ramasamy]

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
> 
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