Dimensionality and validity of the content knowledge for teaching construct using cognitive diagnostic modeling and known groups comparisons

This study compared undergraduate physics majors and secondary physics teachers on two fundamental aspects of content knowledge for teaching (CKT). Since these groups have similar content knowledge (CK) backgrounds, they should have similar mastery of physics but should differ on knowledge associated with professional experience (i.e., pedagogical content knowledge [PCK]). Cognitive diagnostic modeling (CDM) was used to assign individuals into groups defined by differences in their physics CK and PCK. Both physics-related background and experience teaching physics were strongly associated with differences in PCK, providing empirical support that CKT is a unique construct associated with both content and professional preparation.