NAME
Text::NSP::Measures::2D::CHI::tscore  Perl module that implements Tscore measure of association for bigrams.
SYNOPSIS
Basic Usage
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"";
}
DESCRIPTION
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 Tscore 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 ttest that was proposed for use in the identification of collocations in large samples of text.
Thus, the Tscore is defined as follows:
m11 = n1p * np1 / npp
Tscore = (n11  m11)/sqrt(n11)
 calculateStatistic()  method to calculate the tscore Coefficient

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.
 getStatisticName()  Returns the name of this statistic

INPUT PARAMS : none
RETURN VALUES : $name .. Name of the measure.
AUTHOR
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 ThomsonMcInnes, University of Minnesota Twin Cities <bthompson@d.umn.edu>
Saiyam Kohli, University of Minnesota Duluth <kohli003@d.umn.edu>
HISTORY
Last updated: $Id: tscore.pm,v 1.11 2006/06/21 11:10:52 saiyam_kohli Exp $
BUGS
SEE ALSO
@incollection {ChurchGHH91,
author={Church, K. and Gale, W. and Hanks, P. and Hindle, D. },
title={Using Statistics in Lexical Analysis},
booktitle={Lexical Acquisition: Exploiting OnLine 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
Copyright (C) 20002006, Ted Pedersen, Satanjeev Banerjee, Amruta Purandare, Bridget ThomsonMcInnes and Saiyam Kohli
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to
The Free Software Foundation, Inc.,
59 Temple Place  Suite 330,
Boston, MA 021111307, USA.
Note: a copy of the GNU General Public License is available on the web at http://www.gnu.org/licenses/gpl.txt and is included in this distribution as GPL.txt.