Text::NSP::Measures::2D::Fisher::twotailed - Perl module implementation of the two-sided Fisher's exact test.
use Text::NSP::Measures::2D::Fisher::twotailed; my $npp = 60; my $n1p = 20; my $np1 = 20; my $n11 = 10; $twotailed_value = calculateStatistic( n11=>$n11, n1p=>$n1p, np1=>$np1, npp=>$npp); if( ($errorCode = getErrorCode())) { print STDERR $errorCode." - ".getErrorMessage(); } else { print getStatisticName."value for bigram is ".$twotailed_value; }
Assume that the frequency count data associated with a bigram <word1><word2> is stored in a 2x2 contingency table:
word2 ~word2 word1 n11 n12 | n1p ~word1 n21 n22 | n2p -------------- np1 np2 npp
where n11 is the number of times <word1><word2> occur together, and n12 is the number of times <word1> occurs with some word other than word2, and n1p is the number of times in total that word1 occurs as the first word in a bigram.
The fishers exact tests are calculated by fixing the marginal totals and computing the hypergeometric probabilities for all the possible contingency tables,
A twotailed fishers test is calculated by adding the probabilities of all the contingency tables with probabilities less than the probability of the observed table. The twotailed fishers test tells us how likely it would be to observe an contingency table which is less probable than the current table.
INPUT PARAMS : $count_values .. Reference of an array containing the count values computed by the count.pl program.
RETURN VALUES : $twotailed .. Twotailed Fisher value.
INPUT PARAMS : none
RETURN VALUES : $name .. Name of the measure.
Ted Pedersen, University of Minnesota Duluth <tpederse@d.umn.edu>
Satanjeev Banerjee, Carnegie Mellon University <satanjeev@cmu.edu>
Amruta Purandare, University of Pittsburgh <amruta@cs.pitt.edu>
Bridget Thomson-McInnes, University of Minnesota Twin Cities <bthompson@d.umn.edu>
Saiyam Kohli, University of Minnesota Duluth <kohli003@d.umn.edu>
Last updated: $Id: twotailed.pm,v 1.13 2008/03/26 17:21:19 tpederse Exp $
@inproceedings{Pedersen96, author = {Pedersen, T.}, title = {Fishing For Exactness}, booktitle = {Proceedings of the South Central SAS User's Group (SCSUG-96) Conference}, year = {1996}, pages = {188--200}, month ={October}, address = {Austin, TX} url = L<http://www.d.umn.edu/~tpederse/pubs.html>}
http://groups.yahoo.com/group/ngram/
http://www.d.umn.edu/~tpederse/nsp.html
Copyright (C) 2000-2006, Ted Pedersen, Satanjeev Banerjee, Amruta Purandare, Bridget Thomson-McInnes and Saiyam Kohli
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