Characteristics
of a Good Test: Reliability
A measure of the
consistency with which the question, test or examination produces the same
results under different, but comparable
conditions. A reliable assessment item gives reproducible scores with similar
populations of students, and is therefore as independent of the characteristics
and vagaries of individual markers as possible. This is often difficult to
achieve in practice. That is called reliability test.
It is obviously important
to have reasonably reliable assessment procedures when a large number of
individual markers assess the same question (e.g in national school examinations
or with many postgraduates marking lab work). A student answer which receives a
score of 75 per cent from one marker and 35 per cent from another, for example,
reveals a patently unreliable assessment procedure.
To help produce
reliability, the questions which comprise an assessment should (ideally) test
only one thing at a time and give the candidates no choice. The assessment
should also adequately reflect the desired outcomes of the teaching unit. Note
that the reliability and validity factors in an assessment are in no way
directly linked - a test or examination, for example, may be totally reliable
and yet have very low validity, and vice versa.
.
No test will be
absolutely consistent. Even physical measurements such as height and weight
will vary from measurement to measurement, and psychological measurements are
bound to be even less consistent. Nonetheless, it is necessary to make
psychological tests as reliable as possible.
There are several ways to
measure the reliability of a test. The first method is called test-retest reliability, and it involves giving the same test to the same people at different
times. The closer the scores are for the individual at the different times, the
more reliable the test is. The problem with test-retest reliability is that
people may remember the test from taking it earlier and therefore give the same
answers. This may inflate the reliability scores of the test.
Another method of testing
reliability is called split-half reliability. The measurement of reliability compares the scores on two halves of
the same test to measure reliability.
Yet another method of measuring the reliability of a test is called equivalent form reliability. In this method, two different forms of a test are administered to the
same people, and the correlation between the scores on the two tests is
calculated.
.
-->
http://academics.tjhsst.edu/psych/oldPsych/ch11/11.htm
No comments:
Post a Comment