While major test publishers randomly select school districts for their national norming studies, a survey of "accepting" and "declining" districts supports the hypothesis that self-selection bias results in overrepresentation of districts which already use a specific publisher's tests or instructional materials. (Author/BW)

The following information on the development of the 1978 Metropolitan Achievement Tests (MAT), fifth edition, is given; the purpose and importance of item analysis, steps preceding item tryout, characteristics of the sample population, and data obtained. Item analysis allows elimination of undesirable items, adjustment of the difficulty level of…