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Statistics::TTest - Perl module to perform T-test on 2 independent samples
use Statistics::PointEstimation; use Statistics::TTest; my @r1=(); my @r2=(); my $rand;
for($i=1;$i<=32;$i++) #generate a uniformly distributed sample with mean=5
{
$rand=rand(10);
push @r1,$rand;
$rand=rand(10)-2;
push @r2,$rand;
}
my $ttest = new Statistics::TTest; $ttest->set_significance(90); $ttest->load_data(\@r1,\@r2); $ttest->output_t_test(); $ttest->set_significance(99); $ttest->print_t_test(); #list out t-test related data
#the following thes same as calling output_t_test()
my $s1=$ttest->{s1}; #sample 1 a Statistics::PointEstimation object
my $s2=$ttest->{s2}; #sample 2 a Statistics::PointEstimation object
print "*****************************************************\n\n";
$s1->output_confidence_interval('1');
print "*****************************************************\n\n";
$s2->output_confidence_interval('2');
print "*****************************************************\n\n";
print "Comparison of these 2 independent samples.\n";
print "\t F-statistic=",$ttest->f_statistic()," , cutoff F-statistic=",$ttest->f_cutoff(),
" with alpha level=",$ttest->alpha*2," and df =(",$ttest->df1,",",$ttest->df2,")\n";
if($ttest->{equal_variance})
{ print "\tequal variance assumption is accepted(not rejected) since F-statistic < cutoff F-statistic\n";}
else
{ print "\tequal variance assumption is rejected since F-statistic > cutoff F-statistic\n";}
print "\tdegree of freedom=",$ttest->df," , t-statistic=T=",$ttest->t_statistic," Prob >|T|=",$ttest->{t_prob},"\n";
print "\tthe null hypothesis (the 2 samples have the same mean) is ",$ttest->null_hypothesis(),
" since the alpha level is ",$ttest->alpha()*2,"\n";
print "\tdifference of the mean=",$ttest->mean_difference(),", standard error=",$ttest->standard_error(),"\n";
print "\t the estimate of the difference of the mean is ", $ttest->mean_difference()," +/- ",$ttest->delta(),"\n\t",
" or (",$ttest->lower_clm()," to ",$ttest->upper_clm," ) with ",$ttest->significance," % of confidence\n";
This is the Statistical T-Test module to compare 2 independent samples. It takes 2 array of point measures, compute the confidence intervals using the PointEstimation module (which is also included in this package) and use the T-statistic to test the null hypothesis. If the null hypothesis is rejected, the difference will be given as the lower_clm and upper_clm of the TTest object.
Yun-Fang Juan , Yahoo! Inc. (yunfang@yahoo-inc.com)
Statistics::Descriptive Statistics::Distributions Statistics::PointEstimation