On 07 Jan 2016, at 08:31 , David Winsemius <dwinsem...@comcast.net> wrote:
On Jan 6, 2016, at 8:16 PM, li li <hannah....@gmail.com> wrote:
Hi all,
Is there an R function that does exact randomization trend test?
For example, consider the 2 by 5 contingency table below:
dose0 dose 0.15 dose 0.5 dose 1.5 dose 5 row
margin
Yes 4 3 4 5
8 24
No 4 5 4 3
0 16
col sum 8 8 8 8
8 40
Your data presentation has been distorted by your failure to post in
plain text. Surely you have been asked in the past to correct this issue?
To do the exact trend test, we need to enumerate all the contingency
table
with the
row and column margins fixed.
Er, how should that be done? A trend test? What is described above would
be a general test of no association rather than a trend test. Please use
clear language and be as specific as possible if you choose to respond.
Find the probability corresponding to
obtaining
the corresponding contingency tables based on the multivariate
hypergeometric distribution. Finally the pvalue is obtained by adding
relevant probabilities.
If there is a trend under consideration, then I do not understand such a
trend would be modeled under a hypergeometric distribution? A hypergeometic
distribution would suggest no trend, at least to my current understanding.
I'd expect that there is such a beast as a noncentral multivariate
hypergeometric (for the 2x2 case that is what we use to get the CI for the
odds ratio), but usually, one just wants the null distribution of the test
statistic.
Is there an R function that does this? if not, I am wondering whether
it is
possible to
enumerate all possible contingency tables that has column sun and row
sum
fixed?
Wel, yes, that is possible and routinely done with `fisher.test`, but it
is up to you to describe how that activity leads to a trend test.
If you assume Poisson distributed errors a trend test is fairly easy to
construct with glm.
Or, more to the point, there is prop.trend.test(). Neither are exact
tests, though.
I think package "coin" may something relevant.
-pd
--
David.
Thanks very much!!
Hanna
[[alternative HTML version deleted]]
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David Winsemius
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______________________________________________
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--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
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Email: pd....@cbs.dk Priv: pda...@gmail.com
