1 /* statistics/ttest_source.c 2 * 3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Jim Davies, Brian Gough 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 3 of the License, or (at 8 * your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, but 11 * WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 * General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 18 */ 19 20 double 21 FUNCTION(gsl_stats,ttest) (const BASE data1[], 22 const size_t stride1, const size_t n1, 23 const BASE data2[], 24 const size_t stride2, const size_t n2) 25 { 26 /* runs a t-test between two datasets representing independent 27 samples. Tests to see if the difference between means of the 28 samples is different from zero */ 29 30 /* find means for the two samples */ 31 const double mean1 = FUNCTION(gsl_stats,mean) (data1, stride1, n1); 32 const double mean2 = FUNCTION(gsl_stats,mean) (data2, stride2, n2); 33 34 /* find pooled variance for the two samples */ 35 const double pv = FUNCTION(gsl_stats,pvariance) (data1, stride1, n1, data2, stride2, n2); 36 37 /* calculate the t statistic */ 38 const double t = (mean1 - mean2) / (sqrt (pv * ((1.0 / n1) + (1.0 / n2)))); 39 40 return t; 41 } 42 43