A Comparison of Ideal-Point and Dominance Response Processes with a Trust in Science Thurstone Scale

The purpose of this study is to compare the dominance and ideal-point response process models for a trust in science measure developed from Thurstone’s (Am J Sociol 33(4):529–554, 1928; Psychol Rev 36(3):222–241, 1929) scaling procedures. The trust in science scale was scored in four different ways: (1) a dominance response approach using observed scores, (2) a dominance response approach using model-based trait estimates, (3) an ideal-point response observed score approach using Thurstone scoring, and (4) an ideal-point response approach using model-based trait estimates. Comparisons were made between the four approaches in terms of psychometric properties and correlations with political beliefs, education level, and beliefs about scientific consensus in a convenience sample of 401 adults. Results suggest that both the ideal-point and two-parameter IRT models fit equally well in terms of overall model fit. However, two items demonstrated poor item fit in the two-parameter model. Correlations with political beliefs, education level, and science-related items revealed very little differences in magnitude across the four scoring procedures. This study shows support for the flexibility of the ideal-point IRT model for capturing non-ideal-point response patterns. The study also demonstrates the use of using IRT to examine item parameters and item fit.