We present a concept inventory to evaluate student understanding of size, scale, and structure concepts in the astronomical context. Students harbor miscon- ceptions regarding these concepts, and these misconceptions often persist even after instruction. Evaluation of these concepts prior to as well as after instruction can ensure misconceptions are addressed. Currently, no concept inventories focus exclusively on these geometrical ideas, so we have developed the Size, Scale and Structure Concept Inventory (S3CI). In fall 2013, we piloted a 24-item version of the S3CI in an introduc- tory astronomy course at a small private university. We performed an item analysis and estimated the internal consistency reliability for the instrument. Based on these anal- yses, problematic questions were revised for a second version. We discuss the results from the pilot phase and preview our updated test in this work.
A valid and reliable concept inventory has the potential to accurately evaluate undergraduates’ understanding of size, scale, and structure concepts in the astronomical context, as well as assess conceptual change after targeted instruction. Lessons learned in the evaluation of the initial version of the S3CI can guide future development of this and other astronomical concept inventories. Instructors interested in participating in the ongoing development of the S3CI should contact the authors.