Text::NSP::Measures::2D::CHI::tscore - Perl module that implements T-score measure of association for bigrams.
use Text::NSP::Measures::2D::CHI::tscore; my $npp = 60; my $n1p = 20; my $np1 = 20; my $n11 = 10; $tscore_value = calculateStatistic( n11=>$n11, n1p=>$n1p, np1=>$np1, npp=>$npp); if( ($errorCode = getErrorCode())) { print STDERR $errorCode." - ".getErrorMessage()."\n""; } else { print getStatisticName."value for bigram is ".$tscore_value."\n""; }
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 T-score is defined as a ratio of difference between the observed and the expected mean to the variance of the sample. Note that this is a variant of the standard t-test that was proposed for use in the identification of collocations in large samples of text.
Thus, the T-score is defined as follows:
m11 = n1p * np1 / npp T-score = (n11 - m11)/sqrt(n11)
INPUT PARAMS : $count_values .. Reference of an hash containing the count values computed by the count.pl program.
RETURN VALUES : $tscore .. tscore value for this bigram.
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: tscore.pm,v 1.11 2006/06/21 11:10:52 saiyam_kohli Exp $
@incollection {ChurchGHH91, author={Church, K. and Gale, W. and Hanks, P. and Hindle, D. }, title={Using Statistics in Lexical Analysis}, booktitle={Lexical Acquisition: Exploiting On-Line Resources to Build a Lexicon}, editor={Zernik, U.}, year={1991}, address={Hillsdale, NJ}, publisher={Lawrence Erlbaum Associates} url = L<http://www.patrickhanks.com/papers/usingStats.pdf>}
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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