Content and form characteristics that predict discriminating power in personality items: an item response theory-based analysis

In two personality item pools that measure extraversion and neuroticism, the relations between three groups of itemmetric properties and the estimated discrimination indexes according to the two-parameter model are assessed. The itemmetric properties, which are conceptualized as dimensions, are: verbal complexity, ambiguity, and trait indicativity, and the hypotheses concerning their impact on the discriminating power are derived from a processing-stage model. The dimension of trait indicativity shows the clearest relations with the discriminating power in the expected direction. The implications of the results in the construction of personality measures are discussed.