person’s performance on a test item is determined by the underlying trait of that person and by the characteristics of the test item, which includes two key parameters, item threshold and item discrimination. Item threshold is the level at which the underlying trait corresponds to a 50 percent chance of endorsing the item. Higher item thresholds indicate greater severity. Item discrimination (illustrated by slopes) indicates the accuracy of an item in distinguishing individuals with different levels of severity along the underlying trait continuum. These parameters are presented graphically with an item response curve (IRC) for each of the AUD symptom criteria. In addition, item information curves that correspond to these IRCs were summed to produce test information curves (TIC), which are also presented graphically. TICs embody the overall precision of these criteria in assessing a given level of the AUD severity (latent trait).
