Brownell Exp Design

(The FASEB Journal.2014;28:531.10)

Building a learning progression of undergraduate students’ conceptions of two important aspects of experimental design: sample size and repetition of experiments

Sara Brownell,1 Mary Pat Wenderoth2 and Alison Crowe2
1School of Life Sciences Arizona State University Tempe AZ United States
2Biology University of Washington Seattle WA United States

Learning progressions are research-based models of how core ideas are formed over time, often focused on student ‘ways of thinking’ (Duncan and Rivet 2013, Songer et al. 2009). We currently lack a learning progression for undergraduate biology majors’ understanding of experimental design. In order to better understand student thinking about experimental design, we had undergraduate students in introductory biology complete a worksheet with two questions: (a) Why is sample size important and (b) Why was an experiment repeated? Using grounded theory on student responses to these questions, we have identified a set of accurate and inaccurate conceptions. To determine which of these accurate and inaccurate conceptions were “sticky” for undergraduate students, we administered the same questions to advanced students enrolled in upper-level biology courses and calculated the percentage of responses for each conception. By comparing the advanced students and introductory students, we found that significantly more introductory students than advanced students harbor inaccurate conceptions about these two aspects of experimental design. Surprisingly, the gains in accurate conceptions that advanced students had primarily employed statistical reasoning (e.g. to decrease the impact of chance) rather than reasoning based on biological systems (e.g. inherent variation in a population). We are using this work to build an undergraduate learning progressions for experimental design so that we can design ways to better instruct our students.

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