On Wed, May 19, 2010 at 10:53 AM, Will Eagle <will.ea...@gmx.net> wrote: > Dear all, > > how can I get the exact p-value of a statistical test like cor.test() if the > p-value is below the default machine epsilon value of .Machine$double.eps = > 2.220446e-16? > > At the moment smaller p-values are reported as "p-value < 2.2e-16". > .Machine$double.eps <- 1E-100 does not solve this issue, although this value > should be used by the format.pval() function. > > To know the exact p-values down to 1E-200 is very important since I have > multiple tests which require a alpha error-threshold below 2.2E-16. > > Thanks in advance, > > Will >
I would be interested to hear about what kind of multiple testing you're doing. Genetics? Intuitively, requiring that small p-values would seem to throw away most any interesting results that are not simply errors in your data - are you sure that there's not a better way of thinking about your problem? >From a practical standpoint, I would be sceptical about the ability of most R-algorithms to generate theoretically valid p-values of such a small order..... Best regards, Gustaf -- Gustaf Rydevik, M.Sci. tel: +46(0)703 051 451 address:Essingetorget 40,112 66 Stockholm, SE skype:gustaf_rydevik ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
