SINGLE CASE EXPERIMENTALDESIGNS

(INTRA-SUBJECT REPLICATION DESIGNS)

Evaluation of treatment effects inclinical and applied research

Developed in the field ofApplied Behaviour Analysis

Shaping of appropriate verbal responses ina four-year old autistic boy by means of

electric shock

SINGLE CASE EXPERIMENTAL DESIGNS

Idiographic (usually – sort of)

Avoids the problem of within-groupvariability in nomothetic designs

SINGLE CASE EXPERIMENTAL DESIGNS

Pre-test Post-test

Treatment

Control

between-group variabilitywithin-group variability

F =

Pre-test Post-test

Treatment

Control

between-group variabilitywithin-group variability

F =

If within-group variability is high:

Might find no statistically significant differencebetween groups, even though the treatment workswell for some individuals

Aim of single case designs is to demonstratethat the treatment caused

any observed change in behaviourand not some other factor

Rule out potential independent variables

(threats to validity)

If X, then Yand

If not X, then not Y

Evidence for the efficacy of a treatment isobtained if and only if a change in behaviour

is observed when and only whenthe treatment is applied

BASELINE

TREATMENT

FOLLOW-UP

BASELINE

TREATMENT

FOLLOW-UP

VISUAL INSPECTION OF DATA

Behavioural Assessment:

Target behaviours clearly defined

Inter-rater reliability assessed, where appropriate

Stable baselines established

BASELINE

TREATMENT

FOLLOW-UP

VISUAL INSPECTION OF DATA

BASELINE

TREATMENT

FOLLOW-UP

VISUAL INSPECTION OF DATA

If X, then Y; but notif not X, then not Y

ABAB (REVERSAL) DESIGNS

BASELINE A

TREATMENT PHASE B

TREATMENT PHASE B

REVERSAL PHASE A

A B A B

A B A B

MULTIPLE BASELINE DESIGNS

Do not require reversal phase Multiple baselines across:Participants

BehavioursSituations

Multiplebaselinesacross

participants

Requires independenceof participants

Pates et al. (2005)

Effects of music on flow statesand shooting performance amongnetball players

Flow data

Pates et al. (2005)

Effects of music on flow statesand shooting performance amongnetball players

Performance data

Callow & Waters (2005)

Effect of kinaesthetic imageryintervention on sport confidenceof flat-race horse jockeys

Multiplebaselinesacross

behaviours

Requires independenceof behaviours

SWAIN & JONES (1995)

Effects of goal-setting intervention on selectedbasketball skills

Multiple baselines across participants and behaviours:

Offensive rebounds

Defensive rebounds

Steals

Turnovers

SWAIN & JONES (1995)

Participants assessed on performance across8 games and then selected one aspect ofperformance to work on

Intervention: Individualisedgoal-settingprocedure

MORE ADVANTAGES

Complex intervention packages

Comparing different interventions

Improving interventions

MORE ADVANTAGES

POTENTIAL LIMITATIONS

How many ‘successful’ interventions do we need

to be confident that the treatment

is having an effect?

How many ‘failures’ can we tolerate?

Internal validity

POTENTIAL LIMITATIONS

External validity

How many times do we need to replicate

the findings in order to be able

to generalise?

POTENTIAL LIMITATIONS

Non-specific treatment effects

Attention effects, participant expectations

of benefit and demand characteristics

of the experimental situation may be

particularly problematic in single case designs

POTENTIAL LIMITATIONS

Trends towards change during baselinecan make interpretation difficult

Single case designs are idiographic and

yet quantitative. We gain some of the richness

and in-depth understanding of qualitative

research methods whilst being able to quantify

change and maintain a relatively objective

stance towards the data and its interpretation

CONCLUSION