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 Baseline (A)Treatment (B) X= 2.12X= 6.71 sd=.74sd= 3.52

B1.76 B1.96 B1.50 B2.01 B3.94 Tx 3.64 Tx 3.65 Tx 4.00 Tx 6.51 Tx 7.20 Tx 9.70 Tx11.83 Tx 2.01 Tx 6.51 Tx12.00

Sources of Effect Size for SSD 1.Standard Mean Difference Subtract the mean of the baseline phase from the mean of the intervention phase Divided by standard deviation of baseline X tx - X b d = sd b

Sources of Effect Size for SSD X tx - X b d = sd b d = =

SMD all = 7.23SMD 3 = 8.25

d = 6.20

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)

PND = 7/10 = 70%

Interpretation for PND PND scale –90%+ = Highly Effective –70%-90%= Moderately Effective –50%-70%= Minimally Effective –>50% = Ineffective

Sources of Effect Size SSD 3.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)

Simulation Dataset Baseline (A)Treatment (B) X= 1.77 X= 6.84

MBR = x 100 = (mean percent reduction)

Interpretation for MBR Relative effect: 200% is greater than 100% ???? There is no standard for magnitude of effect.