What are the pros and cons of a between-subjects design?

While a between-subjects design has fewer threats to internal validity, it also requires more participants for high statistical power than a within-subjects design.

Advantages:

  • Prevents carryover effects of learning and fatigue.
  • Shorter study duration.

Disadvantages:

  • Needs larger samples for high power.
  • Uses more resources to recruit participants, administer sessions, cover costs, etc.
  • Individual differences may be an alternative explanation for results.