Parallel Forms Reliability

            Parallel Forms reliability is a form of reliability estimate. Two tests are created using the same material and the same format, i.e. multiple choice or fill in the blank. A large set of test questions must be constructed over the same material, similar in item difficulty and then randomly divided among two tests. Both tests are given to the same group of people at the same time, with just enough of a break between test administrations to prevent fatigue. Parallel forms reliability is used to determine what questions are the best ones to ask when developing tests.

            The purpose of the administration procedure is test security. It is believed that the correlation between the two scores on the two tests equal the estimate of test reliability. In other words the two tests can be administered independently of each other and result in equal measurements. Parallel reliability forms may be used in combination with other reliability estimates such as split half reliability.

            As with all forms of measurement, limitations do exist.  Disadvantages to using the parallel forms reliability as an estimate of test reliability are administering two tests to the same group of people and financial expense. When giving two tests to the same group of people, scores may be affected by motivation and fatigue. Creating two forms of a test with the same content and equal level of item difficulty is time consuming. Costs add up. Administering two tests to a sample group can become expensive. However, administering the two tests at the same time to the same group of people does minimize the memorization of the content on the first test to use on the second.

References

Cohen, R.J., Swerdlik, M.E., & Phillips, S.M. (1996). Psychological testing and assessment. Mountain View, CA: Mayfield Publishing Company.

Parallel forms reliability. (n.d.) Retrieved February 19, 2010 from changingminds.org: http://changingminds.org/explanations/research/design/types_reliability.htm.

Parallel forms reliability. (n.d.) Retrieved February 19, 2010 from proftesting.com: www.proftesting.com/test_topics/pdfs/test_quality_reliability.pdf

Parallel forms reliability. (n.d.) Retrieved February 19, 2010 from about.com:  http://psychology.about.com/od/researchmethods/f/reliabiltydef.htm