Item Response Theory Analysis of the TriPM
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This study investigated item and scale functioning in the Triarchic Psychopathy Measure (TriPM) using an item response theory analysis. TriPM data collected from 937 (410 men, 527 women) college students and community members was analyzed. A graded response model was utilized to analyze the 58 self-report items comprising the TriPM’s three scales. Each scale was found to include some items that did not function well at differentiating between respondents possessing varying levels of the trait being measured by that scale. Across all three scales, 40 totals items yielded evidence of significantly different responding between men and women possessing similar levels of the underlying trait. Item and scale performance was highly consistent between two scales, disinhibition and meanness, but distinct from the third scale, boldness. The analysis also found evidence that scoring format (i.e. directly scored vs. reverse-scored) impacted item functioning, especially when the given scale included a large majority of one scoring type. Overall, the IRT and DIF results suggest that the TriPM effectively identifies disinhibition and meanness in individuals possessing high levels of those traits, and boldness at lower levels, but does not seem to identify these traits equally in men and women.