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10.0 Systematic Reviews for Single Subject Designs.

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Presentation on theme: "10.0 Systematic Reviews for Single Subject Designs."— Presentation transcript:

1 10.0 Systematic Reviews for Single Subject Designs

2 Source of Effect Size For SSD 3 Classes Typically Reported –Standard Mean Difference –Percentage of Non-Overlapping Data (PND) –Regression

3 Baseline (A) Intervention (B)

4 Simulation Dataset Baseline (A)Treatment (B) 1.76 3.64 1.96 3.65 1.50 4.00 2.01 6.51 3.94 7.20 9.70 11.83 2.01 6.51 12.00 X= 2.12X= 6.71 sd=.74sd= 3.52

5 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

6 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

7 Sources of Effect Size for SSD X tx - X b d = sd b 6.71-2.12 d = = 6.20.74

8 SMD all = 7.23SMD 3 = 8.25

9 d = 6.20

10 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

11 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)

12 PND = 7/10 = 70%

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

14 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)

15 Simulation Dataset Baseline (A)Treatment (B) 1.76 3.64 1.96 3.65 1.50 4.00 2.01 6.51 3.94 7.20 9.70 11.83 2.01 6.51 12.00 X= 1.77 X= 6.84

16 1.77 - 6.84 MBR = x 100 = 286.0 1.77 (mean percent reduction)

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


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