An approximately standardized person test for assessing consistency with a latent trait model

Latent trait models predict that an examinee's ability level is invariant over subtests of the total test, that is, that all subtests measure the same latent trait. Three statistics are proposed and evaluated as significance tests of this invariance hypothesis. They are computed on the basis of a single response vector and are asymptotically standardized, that is, their conditional distributions given a particular level of ability do not depend upon the absolute value of the examinee's ability parameter. In a Monte Carlo study, one of the statistics turned out to perform satisfactorily for test lengths of 80 items. The use of the test statistic is illustrated in two applications.