PSYCHOMETRIC MODELS OF STUDENT CONCEPTIONS IN SCIENCE - RECONCILING QUALITATIVE STUDIES AND DISTRACTOR-DRIVEN ASSESSMENT INSTRUMENTS

We stand poised to many the fruits of qualitative research on children 's conceptions with the machinery of psychometrics. This merger allows us to build upon studies of limited groups of subjects to generalize to the larger population of learners. This is accomplished by reformul ating multiple choice tests to reflect gains in understanding cognitiv e development. This study uses psychometric modeling to rank the appea l of a variety of children's astronomical ideas on a single uniform sc ale. Alternative conceptions are captured in test items with highly at tractive multiple choice distracters administered twice to 1250 8th th rough 12th-grade students at the start and end of their introductory a stronomy courses. For such items, an unusual psychometric profile is o bserved-instruction appears to strengthen support for alternative conc eptions before this preference eventually declines. This lends support to the view that such ideas may actually be markers of progress towar d scientific understanding and are not impediments to learning. This m ethod of analysis reveals the ages at which certain conceptions are mo re prevalent than others, aiding developers and practitioners in match ing curriculum to student grade levels. This kind of instrument, in wh ich distracters match common student ideas, has a profoundly different psychometric profile from conventional tests and exposes the weakness evident in conventional standardized tests. Distractor-driven multipl e choice tests combine the richness of qualitative research with the p ower of quantitative assessment, measuring conceptual change along a s ingle uniform dimension. (C) 1998 John Wiley & Sons, Inc.