Equating

Test equating traditionally refers to the statistical process of determining comparable scores on different forms of an exam.

It is the process of equating the units and origins of two scales on which the abilities of students have been estimated from results on different tests.

Equating analyses are performed to address this very issue, so that scores are as fair as possible.

It is common in educational assessment to employ tests in order to assess different groups of students with the intention of establishing a common scale by equating the origins, and when appropriate also the units, of the scales obtained from response data from the different tests.

In terms of item response theory, equating is just a special case of the more general process of scaling, applicable when more than one test is used.

The mean and standard deviation of the scale locations of the group on the two tests are equated using a linear transformation.

While mean equating is attractive because of its simplicity, it lacks flexibility, namely accounting for the possibility that the standard deviations of the forms differ.