[R] Re: [Rd] (no subject)
huber at ebi.ac.uk
Sun Oct 31 10:42:03 CET 2004
Dear Fang Lai,
you have sent your mail to both r-devel and r-help. Please do not do this,
but decide for one. Cross-posting just creates unnecessary and unpleasant
junk-mail to many people.
Furthermore, neither the r-devel nor the r-help mailing lists are intended
as replacements to taking a basic statistics course or reading the
software manuals - rather, as supplement and last resort. The answers are
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yourself also make at least a minimal effort before going off the mailing
European Bioinformatics Institute
European Molecular Biology Laboratory
Cambridge CB10 1SD
Phone: +44 1223 494642
<quote who="fang lai">
> Dear all,
> I have several questions regarding fisher.test() in
> R, and I'd highly appreciate any help with it.
> I have a group of observations, each having people's
> income, and an indicator of whether selected in or out
> a program. I want to test the difference between
> income of people who are in and out.
> Because the distribution is far from normal, I decide
> to use the fisher's exact test, using either mean or
> rank as statistics.
> Question 0 is: Can I do this test using fisher.test()
> in R?
> If so,
> My first question is: Does fisher.test() offer an
> option to choose the statistics? Actually it is not
> clear from the help to me what statistics it uses.
> Does it just compare the mean of people in and out of
> the program?
> My second question is: when the group is large, I
> always receive a warning message such as "Fisher exact
> result might not be right" when I set "hybrid=T".
> When I set "hybrid=F", it does return a result of
> p-value without warning message. I wonder if this
> p-value is reliable or not. And, how does it get the
> approximation of p-value when "hybrid=F"? Ideally, it
> should randomly draw, say 1000 times, from the full
> sets of permutation of assignment, and get an
> approximate p-value--is this the way it works in
> fisher.test( ) in R? If not, does it use another test,
> or some other measure of approximation?
> My last question is: when the group is small enough,
> will it calculates the exact probabilities even if
> Many thanks,
> Lai, Fang
> PhD candidate
> University of California, Berkeley
> Department of Agricultural and Resource Economics
> 314 Giannini Hall, Berkeley, CA 94720-3310
> tel: (510) 643 - 5421(O)
> (510) 847 - 9811(Cell)
> fax: (510) 643 - 8911
> email: lai at are.berkeley.edu
> R-devel at stat.math.ethz.ch mailing list
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