[R] Re: [Rd] (no subject)

[Wolfgang Huber]

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
provided by unpaid voluntary contributors, who appreciate that you
yourself also make at least a minimal effort before going off the mailing
list.

Best wishes
 Wolfgang

-------------------------------------
Wolfgang Huber
European Bioinformatics Institute
European Molecular Biology Laboratory
Cambridge CB10 1SD
England
Phone: +44 1223 494642
Http:  www.dkfz.de/abt0840/whuber
-------------------------------------

<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
> hybrid=F?
> Many thanks,
>
> Fang
>
> =====
> 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
> http://www.are.berkeley.edu/jobmarket/fang.html
>
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