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10.0 Systematic Reviews for Single Subject Designs. Source of Effect Size For SSD. 3 Classes Typically Reported Standard Mean Difference Percentage of Non-Overlapping Data (PND) Regression. Baseline (A). Intervention (B). Simulation Dataset. Sources of Effect Size for SSD.
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Source of Effect Size For SSD 3 Classes Typically Reported • Standard Mean Difference • Percentage of Non-Overlapping Data (PND) • Regression
Baseline (A) Intervention (B)
Sources of Effect Size for SSD • Standard Mean Difference • Subtract the mean of the baseline phase from the mean of the intervention phase • Divided by standard deviation of baseline Xtx- Xb d = sdb
Sources of Effect Size for SSD Xtx- Xb d = sdb 6.71-2.12 d = = 6.20 .74
SMD3= 8.25 SMDall= 7.23
Interpretation for SMD • A 6 standard deviation advantage for the treated participants • .8 standard deviations=large effect • The SMD for SSD is not the same metric as the SMD for group comparisons
Sources of Effect Size For SSD 2. Percentage of Non-Overlapping Data (PND) • Identify the highest baseline point • Count the number of intervention points that exceed the highest baseline point (non-overlapping). • Calculate the proportion of non-overlapping to total number of intervention points (can’t use if baseline has a zero point)
Interpretation for PND PND scale • 90%+ = Highly Effective • 70%-90%= Moderately Effective • 50%-70%= Minimally Effective • >50% = Ineffective
Sources of Effect Size SSD • Mean Baseline Reduction (MBR) • Subtract the average of last 3 Tx points from the average of the last 3 baseline points • Divide by the average of the last 3 baseline points • Multiply by 100 for percent of baseline reduction (MBR)
1.77 - 6.84 MBR= x 100 = 286.0 1.77 (mean percent reduction)
Interpretation for MBR • Relative effect: 200% is greater than 100% • ???? There is no standard for magnitude of effect.