Individualized Analytics: Within-Person and Idiographic Analysis

Abstract

Two research paradigms are commonly used: between-person (often known as nomothetic or group-based) and within-person analysis. The between-person approach captures data across different people and gathers their variations, hence the name of between-person. Within-person research captures data within the same person, gathering these variations across times or occasions and thus the name. These two approaches converge if and only if ergodicity holds. Ergodicity claims that people are similar (so that it does not matter whom to measure) and they do not change over time (so that it does not matter when to measure). However, this is often not the case in education research. Thus, the within-person approach is needed. When within-person analysis is conducted on a single person (N=1), it is known as idiographic analysis. In this chapter, we describe the main characteristics of each approach, as well as common data sources and methods used in within-person and idiographic analysis. © 2026 The Editor(s) (if applicable) and The Author(s).