Developmental Research MethodsTopic 12: Small N Research

04/10/2023CEDP 321/322 Ryan Sain, Ph.D. 1

Single Subject (small n)Problems with group analysis

◦Individual differences are ignored These are important factors!

◦This logic is based on farming analysis!

Single subject logicThe logic of single subject is high

levels of internal validity (control) then replication.◦Systematic replication◦Direct replication

Experimental Single Subject DesignUsing 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

Simple AB Design

Baseline Intervention

Reversal design• Shifting conditions – must be

something that is not a permanent change

• Baseline (Stability)• Treatment (stability)• Baseline (stability)• ABA designs• Ethics

ABA Design

Baseline Intervention Baseline 2

ABAB DesignFull reversalCannot be permanent changeEthicsShowing effects across people

ABAB (full reversal) design

Baseline Intervention Baseline 2 Intervention

ABAC Design

Baseline Intervention Baseline 2 Intervention 2

Multiple BaselineSeveral individualsBaselines overlap to control for

environmental variables.The treatment is then introduced

at different times for eachIf the behavior changes in each

person at the treatment time, then the IV has the effect.

Multiple BaselineBaseline Intervention

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