Between-subjects designs
Compare conditions experienced by different participants
In a between-subjects design, different participants contribute observations to different conditions of the focal manipulation. Random allocation can support causal inference; naturally occurring groups cannot claim that benefit automatically. Avoiding exposure to other conditions can reduce carryover and demand effects, but comparisons must contend with between-person variation and recruitment requirements.
Use when experiencing one condition would alter responses to another, when treatments have lasting effects, or when revealing alternatives would change behaviour. Plan comparable groups and adequate independent replication.
Strengths
- Avoids within-person carryover between focal conditions
- Can keep alternative manipulations concealed
Limitations
- Between-person variability reduces precision
- May require more participants than a comparable repeated design
Know the boundary
Between-subjects describes who receives conditions; it does not imply randomisation or guarantee a causal design.