Small N Designs
Single Subject Research Design (SSRD) involves studying a single individual or system by taking repeated measurements of 1 or more dependent variables and systematically applying & sometimes, withdrawing or varying the independent variable.
Small N Designs
• Designs that involve a very small number of participants
• Rather than reporting measures of central tendency, focus is placed on observations of individual scores/behaviors
Practical Reasons for doing Small N Research
• Procedures are costly / time consuming
• Procedures are invasive
• Procedures require intensive training
• Participants are rare / hard to find
Single-Subject Designs
• Goal: Behavior of a single participant must be shown to change as a result of the treatment
• Three Components
1) Target behavior must be operationally defined
2) Baseline level of responding must be established
3) Conduct treatment and monitor behavior
• A-B Designs (baseline → treatment)
• Withdrawal Designs
– A-B-A Design
– A-B-A-B Design
Flood et al. (2002)
Study of ADHD Treatment Efficacy
• Participants: 3 10-year olds previously diagnosed with ADHD, not on meds
• IV: Treatment (single level)
– Ss paired with non-ADHD peer who praises Ss for “on task” behavior and prompts Ss after “off task” behavior
• DV: “Off task” behavior
– Looking away from assigned task for 3 seconds
Multiple Baseline Design
• Three varieties of Multiple Baseline Designs
• Baselines are established for:
(1) 1 type of behavior in 2+ individuals in 1 setting
(2) 2+ types of behaviors in 1 individual in 1 setting
(3) 1 behavior in 1 individual across 2+ settings
Wagaman et al. (1993)
• Multiple Baselines Across Subjects
– (1) 1 behavior in 2+ individuals in 1 setting
• Participants: 8 school children
• IV: “Regulated breathing” treatment
• DV: Stuttering
Criticisms of Small N Designs
• Low external validity
• How do we handle this criticism?
– Evaluate generalizabilty within the design
– Replicate and extend the study
Ethical Considerations
• Withdrawing a treatment that has changed behavior for the good
• Treatments can be controversial
• Case of special needs children
– Benefits of treatment
