Psychometrics & Measurement

Psychometric and measurement expertise

The methodological areas that underpin our research. These describe research expertise and are not a list of commercial services.

Areas of expertise

Models an observed score as true score plus error; supports item difficulty, discrimination, and reliability indices.

Models the probability of a response as a function of a latent trait and item parameters such as difficulty and discrimination.

A measurement model requiring specific objectivity, placing persons and items on a common interval scale.

Estimates score consistency using coefficients such as alpha, omega, test–retest, and IRT-based information.

The accumulation of evidence and theory supporting the intended interpretation and use of scores.

Detects items that behave differently across groups with the same level of the measured trait.

Tests whether a measure has the same meaning and structure across groups, languages, or time points.

Models instruments that measure several related traits, using multidimensional IRT or factor models.

Selects items in real time based on previous responses, achieving precise measurement with fewer items.