Research in Engineering Education Symposium 2011 - rees2009

Universidad Politécnica de Madrid (UPM) Página 592 de 957
Sign test
As an example, let us comment how the sign test should be employed. The sign test is a
nonparametric test that can be used to compare two paired samples. It is very flexible in
application and is especially simple to use and understand.
The sign test is based on the differences of the simple paired values. The only information
used by the sign test is the sign (positive or negative) of each difference. If the differences
are preponderantly of one sign, this is taken as evidence for the alternative hypothesis.
The following example illustrates the use of this test in the Statistical Decision-Making
Laboratory.
The test could, for instance, be used to accept or reject the null hypothesis that the time
employed in the old and new versions of the modules of the laboratory are the same
versus the alternative hypothesis that the times are different, or to test the null hypothesis
that the satisfaction with the old and new versions of the laboratory are the same versus
the alternative hypothesis that they are different, or that the new version is more
satisfactory for the student that the old one.
For instance, let us suppose that there are 11 laboratory groups and that they first follow
the old version of the laboratory in one module and then they follow the new one in the
same module. The next table shows the times employed by the groups, in minutes.
In this example the null hypothesis is:
H0: The time employed by the groups in following the old and new version of the module is
the same. And the alternative hypothesis is:
H1: The time employed by the groups in following the old aversion is larger than the time
for the new version.
The first step is to determine the following counts:
N+ = Number of positive differences
N- = Number of negative differences
Proceedings of Research in Engineering Education Symposium 2011
Madrid, 4 th - 7 th October 2011