Introduction to the measurement of psychological attributes

This article introduces the measurement of psychological attributes, such as intelligence and extraversion. Examples of measurement instruments are discussed, as well as a deterministic measurement model. Error sources that threaten measurement precision and validity are discussed, and also ways to control their detrimental influence. Statistical measurement models describe the random error component in empirical data and impose a structure that, if the model fits the data, implies particular measurement properties for the scale. The well-known Rasch model is discussed along with other models, and using a sample of data collected with 612 students who solved 13 arithmetic tasks it is demonstrated how a scale for arithmetic ability is calibrated. The difference between psychological measurement and physical measurement is briefly discussed.

► I explain the measurement of psychological attributes, such as introversion and arithmetic ability.
► Psychological measurement is done using multi-item tests and questionnaires.
► Psychological measurement suffers from random error and systematic error.
► Test-design choices and statistical measurement models control error.
► Measurement models that fit data enable calibrating a scale, here for arithmetic ability.