Classical Test Theory - Shortcomings of Classical Test Theory

Shortcomings of Classical Test Theory

One of the most important or well known shortcomings of Classical Test Theory is that examinee characteristics and test characteristics cannot be separated: each can only be interpreted in the context of the other. Another shortcoming lies in the definition of Reliability that exists in Classical Test Theory, which states that reliability is "the correlation between test scores on parallel forms of a test". The problem with this is that there are differing opinions of what parallel tests are. Various reliability coefficients provide either lower bound estimates of reliability or reliability estimates with unknown biases. A third shortcoming involves the standard error of measurement. The problem here is that, according to Classical Test Theory, the standard error of measurement is assumed to be the same for all examinees. However, as Hambleton explains in his book, scores on any test are unequally precise measures for examinees of different ability, thus making the assumption of equal errors of measurement for all examinees implausible (Hambleton, Swaminathan, Rogers, 1991, p.4). A fourth, and final shortcoming of the Classical Test Theory is that it is test oriented, rather than item oriented. In other words, Classical Test Theory cannot help us make predictions of how well an individual or even a group of examinees might do on a test item.