## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## 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, 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 file. If not, write to the Free Software Foundation, ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ## usage: [pval, chisq, df] = chisquare_test_independence (X) ## ## Perform a chi-square test for indepence based on the contingency ## table X. ## ## Under the null hypothesis of independence, chisq approximately has a ## chi-square distribution with df degrees of freedom. pval is the ## p-value (1 minus the CDF of this distribution at chisq) of the test. ## ## If no output argument is given, the p-value is displayed. ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Chi-square test for independence function [pval, chisq, df] = chisquare_test_independence (X) if (nargin != 1) usage ("chisquare_test_independence (X)"); endif [r s] = size (X); df = (r - 1) * (s - 1); n = sum (sum (X)); Y = sum (X')' * sum (X) / n; X = (X - Y) .^2 ./ Y; chisq = sum (sum (X)); pval = 1 - chisquare_cdf (chisq, df); if (nargout == 0) printf(" pval: %g\n", pval); endif endfunction

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