SINGLE CASE EXPERIMENTAL DESIGNS (INTRA-SUBJECT REPLICATION DESIGNS)

Evaluation of treatment effects in clinical and applied research Developed in the field of Applied Behaviour Analysis Shaping of appropriate verbal responses in a four-year old autistic boy by means of electric shock SINGLE CASE EXPERIMENTAL DESIGNS

Idiographic (usually – sort of) Avoids the problem of within-group variability in nomothetic designs SINGLE CASE EXPERIMENTAL DESIGNS

Pre-testPost-test Treatment Control between-group variability within-group variability F =

Pre-testPost-test Treatment Control between-group variability within-group variability F =

If within-group variability is high: Might find no statistically significant difference between groups, even though the treatment works well for some individuals

Aim of single case designs is to demonstrate that the treatment caused any observed change in behaviour and not some other factor Rule out potential independent variables (threats to validity)

If X, then Y and If not X, then not Y Evidence for the efficacy of a treatment is obtained if and only if a change in behaviour is observed when and only when the 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 not if not X, then not Y

ABAB (REVERSAL) DESIGNS BASELINE A TREATMENT PHASE B B REVERSAL PHASE A

ABAB

ABAB

MULTIPLE BASELINE DESIGNS Do not require reversal phase Multiple baselines across:Participants Behaviours Situations

Multiple baselines across participants Requires independence of participants

Pates et al. (2005) Effects of music on flow states and shooting performance among netball players Flow data

Pates et al. (2005) Effects of music on flow states and shooting performance among netball players Performance data

Callow & Waters (2005) Effect of kinaesthetic imagery intervention on sport confidence of flat-race horse jockeys

Multiple baselines across behaviours Requires independence of behaviours

SWAIN & JONES (1995) Effects of goal-setting intervention on selected basketball skills Multiple baselines across participants and behaviours: Offensive rebounds Defensive rebounds Steals Turnovers

SWAIN & JONES (1995) Participants assessed on performance across 8 games and then selected one aspect of performance to work on Intervention: Individualised goal-setting procedure

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 baseline can 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