Investigating the Applicability of the Newtonian Gravity Concept Inventory to First Year College Students

Abstract

We report on a study of our students’ understanding of gravity using the Newtonian Gravity Concept Inventory (NGCI). This article is supposed to serve two purposes: as a proof of applicability of the test to first year medical students outside the United States and as a general survey of our students’ understanding of gravity. The motivation for this work came initially from students’ misconceptions of gravity and related topics noticed in classrooms. NGCI has 26 multiple-choice questions probing students’ knowledge of gravity in four different domains: Directionality, Gravity as a force, Independence from other forces and threshold. Results confirmed weak overall performance of the 684 students participated in this study (average score of only 38.48%) with misconceptions related to gravity in all four domains. We were able to prove the applicability of the NGCI to our students through calculations of Classical Test Theory statistics and Cronbach’s alpha. We got a Cronbach’s alpha of 0.68, average difficulty index of 0.62 and average discriminatory index of 0.31 with three questions reported as too difficult based on the acceptable range. The test was given to students twice; before and after any gravity-related instructions in class (pre- and post-test). Post-test results will not be discussed here and left for future articles. In this article, we present the pre-test results and compare it to the original work by the authors of the test on astronomy and physics students.