Publications & Resources
Testing Positive Versus Negative Claims: A Preliminary Investigation of the Role of Cover Story on the Assessment of Experimental Design Skills
Corinne Zimmerman and Robert Glaser
There are many factors that potentially could influence student performance on assessments designed to tap reasoning and problem solving in science. We present results from a preliminary investigation in which we manipulated the cover story of an open-ended assessment that required students to design an experiment. In one version of the cover story, students were asked to design an experiment to test a negative claim (i.e., that tap water is “bad” for plants). In a second version, they were to test a positive claim (i.e., that coffee grinds are “good” for plants). Differences between the two cover stories were found. In the negative condition, students were more likely to suggest controlled designs, to identify the correct independent variable, and to test the claim directly. In the positive condition, students proposed uncontrolled designs and did not select the correct variable to test. When asked to test a positive claim, students seemed to approach the task as if the goal were to test the generality of the claim (by selecting different plant types as the focal variable). Students of all ability levels were influenced by cover story; however, the effect was greatest for students of low ability. Implications for assessment are discussed.
Zimmerman, C., & Glaser, R. (2001). Testing positive versus negative claims: A preliminary investigation of the role of cover story on the assessment of experimental design skills (CSE Report 554). Los Angeles: University of California, Los Angeles, National Center for Research on Evaluation, Standards, and Student Testing (CRESST).