[Octave-bug-tracker] [bug #51927] [octave forge] (statistics) Failure in unit test of ttest function

[Rafael Laboissiere]

URL:
  <http://savannah.gnu.org/bugs/?51927>

                 Summary: [octave forge] (statistics) Failure in unit test of
ttest function
                 Project: GNU Octave
            Submitted by: rlaboiss
            Submitted on: Sun 03 Sep 2017 07:10:57 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: other
        Operating System: GNU/Linux

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Details:

One the unit tests for the ttest function of the statistics package fails on
my system (amd64 Debian with Octave 4.2, statistics 1.3.0):


octave:1> pkg load statistics
octave:2> test ("ttest")
***** test
 x = 8:0.1:12;
 [h, pval, ci] = ttest (x, 10);
 assert (h, 0)
 assert (pval, 1)
 assert (ci, [9.6219 10.3781], 1E-5)
 [h, pval, ci0] = ttest (x, 0);
 assert (h, 1)
 assert (pval, 0)
 assert (ci0, ci)
!!!!! test failed
ASSERT errors for:  assert (pval,1)

  Location  |  Observed  |  Expected  |  Reason
     ()           1            1         Abs err 2.2204e-16 exceeds tol 0


This happens due to a floating-point precision peculiarity, exposed by the
following code:


octave:1> x = 8:0.1:12;
octave:2> mean (x - 10)
ans =    5.4157e-17
octave:3> mean (x) - 10
ans = 0


The attached patch fixes the problem.



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File Attachments:


-------------------------------------------------------
Date: Sun 03 Sep 2017 07:10:57 PM UTC  Name: pval-in-ttest-unit-test.patch 
Size: 481B   By: rlaboiss

<http://savannah.gnu.org/bugs/download.php?file_id=41722>

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