1 /* statistics/ttest_source.c
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Jim Davies, Brian Gough
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.
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.
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.
21 FUNCTION(gsl_stats,ttest) (const BASE data1[],
22 const size_t stride1, const size_t n1,
24 const size_t stride2, const size_t n2)
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 */
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);
34 /* find pooled variance for the two samples */
35 const double pv = FUNCTION(gsl_stats,pvariance) (data1, stride1, n1, data2, stride2, n2);
37 /* calculate the t statistic */
38 const double t = (mean1 - mean2) / (sqrt (pv * ((1.0 / n1) + (1.0 / n2))));