This commentary on the article by Shulman et al. examines what we understand by 'medication errors', what we mean by 'computerized physician order entry (CPOE) systems', how we measure errors, and what types of errors we are 'reducing' with CPOE systems. As the research of Shulman and colleagues highlights, much of the existing research on CPOE systems does not differentiate among: types of med...

We give a historical introduction to item response theory, which places the work of Thurstone, Lord, Guttman and Coombs in a present-day perspective. The general assumptions of modern item response theory, local independence and monotonicity of response functions, are discussed, followed by a general framework for estimating item response models. Six classes of well-known item response models a...