Exploring the class with item response theory

Abstract

This work applied exploratory factor analysis (EFA) and graded Item Response Theory (IRT) to a large sample (N = 4522) of Colorado Learning Attitudes about Science Survey (CLASS) post-test scores. EFA failed to reproduce the factor structure suggested by the authors of the CLASS and strongly supported the alternate 3-factor model suggested by Douglas et al. Graded IRT allowed an examination of the progression from non-expert-like to expert-like beliefs. This progression was generally uniform with a linear relation between the difficulty of each step in the progression. Some items within the factors identified by Douglas et al. had difficulty and discrimination parameters substantially different from other items in the factor suggesting the subscale is not unidimensional. The expert-like latent ability trait estimated by IRT correlated more strongly with measures of physics performance than measures of general academic performance indicating that expert-like beliefs are not a general property of high performing students.