ABSTRACT
It is well known (see also Theorem 8.7.1) that for accurate measurement the difficulty level of a psychological test should be appropriate to the ability level of the examinee. With conventional tests, this goal is achievable for all examinees only if they are fairly homogeneous in ability. College entrance examinations, for example, could provide more reliable measurement at particular ability levels if they did not need to cover such a wide range of examinee talent (see Section 6.10). Furthermore, in many situations it is psychologically desirable that the test difficulty be matched to the examinee's ability: A test that is excessively difficult for a particular examinee may have a demoralizing or otherwise undesirable effect.
