Introduction to Item Response Theory
Psychological measurement is the process of assigning quantitative values as representations of characteristics of individuals or objects, so-called psychological constructs. Measurement theories consist of the rules by which those quantitative values are assigned. Item response theory (IRT) is a measurement theory.
IRT uses a mathematical function to relate an individual’s probability of correctly responding to an item to a trait of that individual. Frequently, this trait is not directly measurable and is therefore called a latent ...