Within-subjects statistics for three or more observations of an outcome is used traditionally to assess change or stability in an outcome across time or "within-subjects" or in the same unit of measurement. Within-subjects statistics for three or more observations are also used to measure how much change or stability occurs across time or within-subjects as a result of a treatment or intervention. At this point when choosing a statistical test for comparing three or more observations of an outcome, the next question to be answered is what the scale of measurement of the outcome. The answer ultimately leads to the correct within-subjects statistical test for three or more observations to answer the research question.
The outcome represents numerical designations or categorical values that describe events or group membership.
The outcome variable is measured using an ordered numerical continuum, such as a Likert scale.
The outcome variable is an actual number that provides both a measure of distance and magnitude due to having a "true zero."
