Psychometric Models of Student Conceptions in Science: Reconciling Qualitative Studies and Distractor-Driven Assessment Instruments

Abstract

We stand poised to marry 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 reformulating multiple choice tests to reflect gains in understanding cognitive development. This study uses psychometric modeling to rank the appeal of a variety of children's astronomical ideas on a single uniform scale. Alternative conceptions are captured in test items with highly attractive multiple choice distractors administered twice to 1250 8th through 12th-grade students at the start and end of their introductory astronomy courses. For such items, an unusual psychometric profile is observed - instruction appears to strengthen support for alternative conceptions before this preference eventually declines. This lends support to the view that such ideas may actually be markers of progress toward scientific understanding and are not impediments to learning. This method of analysis reveals the ages at which certain conceptions are more prevalent than others, aiding developers and practitioners in matching curriculum to student grade levels. This kind of instrument, in which distractors match common student ideas, has a profoundly different psychometric profile from conventional tests and exposes the weakness evident in conventional standardized tests. Distractor-driven multiple choice tests combine the richness of qualitative research with the power of quantitative assessment, measuring conceptual change along a single uniform dimension. © 1998 John Wiley & Sons, Inc.