Item Analysis Platform Overview
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 trait.
To see how IRT relates traits to probabilities, first examine a test question that follows the Guttman “perfect scale” as shown in Figure 7.2. The horizontal axis represents ...

Get JMP 12 Consumer Research now with the O’Reilly learning platform.

O’Reilly members experience live online training, plus books, videos, and digital content from nearly 200 publishers.