THE DEVELOPMENT OF A VALID AND RELIABLE BIOGEOCHEMISTRY CONCEPT INVENTORY

Concept inventories are a commonly used tool to measure conceptual understanding. To date, concept inventories have been published for geology, chemistry, and biology, but no instrument has been designed to measure conceptual understanding at the intersection of those fields. To fill that gap, we constructed a 32-item biogeochemistry concept inventory (BGC-CI). Item response theory analysis, using the Rasch model, shows the BGC-CI is a reliable and valid tool to measure the biogeochemistry knowledge of science majors. Because biogeochemistry is an interdisciplinary field, we were concerned about the unidimensionality of the instrument. However, our analysis showed the BGC-CI to be acceptably unidimensional among science majors. The subject matter included on the BGC-CI is applicable to climate science, oceanography, and environmental science, among other fields. This instrument will allow researchers and teachers to readily quantify learning outcomes in these fields and others that overlap with biogeochemistry.