TTest(3)       User Contributed Perl Documentation       TTest(3)



NNNNAAAAMMMMEEEE
        Statistics::TTest - Perl module to perform T-test on 2 independent samples


SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
        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";


DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
       This is the Statistical T-Test module to compare 2 inde-
       pendent samples. It takes 2 array of point measures, com-
       pute 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.

AAAAUUUUTTTTHHHHOOOORRRR
       Yun-Fang Juan , Yahoo! Inc.  (yunfang@yahoo-inc.com)

SSSSEEEEEEEE AAAALLLLSSSSOOOO
       Statistics::Descriptive Statistics::Distributions Statis-
       tics::PointEstimation



2003-02-07                 perl v5.6.1                   TTest(3)