## Copyright (C) 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] = mcnemar_test (x) ## ## For a square contingency table x of data cross-classified on the row ## and column variables, McNemar's test can be used for testing the null ## hypothesis of symmetry of the classification probabilities. ## ## Under the null, chisq is approximately distributed as chisquare with ## df degrees of freedom, and 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 of the test is displayed. ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: McNemar's test for symmetry function [pval, chisq, df] = mcnemar_test (x) if (nargin != 1) usage ("mcnemar_test (x)"); endif if (! (min (size (x)) > 1) && is_square (x)) error (strcat ("mcnemar_test: ", "x must be a square matrix of size > 1.")); elseif (! (all (all (x >= 0)) && all (all (x == round (x))))) error (strcat ("mcnemar_test: ", "all entries of x must be nonnegative integers.")); endif r = rows (x); df = r * (r - 1) / 2; if (r == 2) num = max (abs (x - x') - 1, 0) .^ 2; else num = abs (x - x') .^ 2; endif chisq = sum (sum (triu (num ./ (x + x'), 1))); pval = 1 - chisquare_cdf (chisq, df); if (nargout == 0) printf (" pval: %g\n", pval); endif endfunction

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