Within-subjects design

As explained in Effective Data Analysis

A within-subjects design compares conditions using the same participants, often by measuring them before and after treatment.

A within-subjects design, also called a repeated-measures design, exposes every participant to every independent-variable condition and repeatedly measures the dependent variable. Researchers commonly compare measurements before and after treatment or across multiple time points. section 3.2.4

Use the design to organize comparisons and interpret its role among related study designs:

• Compare a participant or group with itself across conditions, reducing the focus on differences between separate participant groups. section 3.2.4
• Choose statistical tests designed for repeated measures rather than tests for independent samples used in between-subjects designs. section 3.2.4
• Distinguish a simple within-subjects comparison from cohort and longitudinal designs, which track groups or participants over longer periods. section 3.2.4 section 3.4

Blood pressure before and after treatment

Measure one group’s blood pressure before treatment and again afterward, then evaluate the change within the same participants. section 3.2.4

Figure 3.11 Within-subjects comparisons evaluate differences before and after treatment.

View a visual comparison of within-subjects measurements taken before and after treatment. section 3.2.4

How Effective Data Analysis covers it

How deep it goes

Defines repeated exposure and measurement, distinguishes related designs, and notes different statistical tests without detailing their procedures.

Examples

Uses blood pressure measured before and after treatment as its concrete example.

What it assumes

Assumes independent and dependent variables, experimental conditions, and basic distinctions between participant groups and repeated measurements.

What you can do after

Evaluate treatment-related change by comparing repeated measurements from the same participants across conditions or time points.

How it connects

Connects experiments with between-subjects designs, cohort studies, longitudinal studies, independent variables, and dependent variables.

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Related concepts

• study designkind of · Study design is the planned arrangement of procedures, conditions, measurements, and comparisons used to investigate a question and support valid conclusions.
• between-subjects designcontrasts with · A between-subjects design compares outcomes across separate groups of participants exposed to different conditions.

This explainer was generated by Manning's knowledge graph from the text of Effective Data Analysis. The section links point to the parts of the book it draws on.