Small N research involves studying individual subjects to gain a deeper understanding of individual differences compared to group analysis. It uses experimental single-subject designs where the subject acts as their own control to establish a pattern of behavior and observe how that pattern changes when an intervention is introduced. Common small N designs include the simple AB design with a baseline and intervention phase, reversal designs like ABA to introduce baseline periods again, and multiple baseline designs that stagger the introduction of an intervention across subjects to control for external factors.

1. Developmental Research
Methods
Topic 12: Small N Research
10/1/2014 CEDP 321/322 Ryan Sain, Ph.D. 1

2. Single Subject (small n)
 Problems with group analysis
◦ Individual differences are ignored
 These are important factors!
◦ This logic is based on farming analysis!

3. Single subject logic
 The logic of single subject is high
levels of internal validity (control) then
replication.
◦ Systematic replication
◦ Direct replication

4. Experimental Single Subject
Design
 Using a subject as their own control
◦ If we establish a pattern of responding
◦ change that pattern of responding
 exact moment the IV is present
◦ conclude that it was the IV that had the
effect

5. Simple AB Design
Baseline Intervention

6. Reversal design
• Shifting conditions – must be something
that is not a permanent change
• Baseline (Stability)
• Treatment (stability)
• Baseline (stability)
• ABA designs
• Ethics

7. ABA Design
Baseline Intervention Baseline 2

8. ABAB Design
 Full reversal
 Cannot be permanent change
 Ethics
 Showing effects across people

9. ABAB (full reversal) design
Baseline Intervention Baseline 2 Intervention

10. ABAC Design
Baseline Intervention Baseline 2 Intervention 2

11. Multiple Baseline
 Several individuals
 Baselines overlap to control for
environmental variables.
 The treatment is then introduced at
different times for each
 If the behavior changes in each
person at the treatment time, then the
IV has the effect.

12. Multiple Baseline
Baseline Intervention
Toks
Home
Qudsia
Toks
School
Toks
Toks
Daycare
Tusu