• Between-subjects designs include control or comparison groups and permit random assignment to groups, but large individual differences between participants may make it difficult to find effects.
  
  
• Repeated-measures designs require fewer participants and typically have more statistical power, but there may be practice or carryover effects that influence the results.
  
  
• Practice and carryover effects can be avoided by counterbalancing conditions.
  
  
• Factorial designs have more than one independent variable. Mixed factorial designs have at least one between-subjects factor and one within-subjects factor.
  
  
• Each design has a structural model that guides statistical analysis.

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