Calculating Effect Sizes for Single Subject Designs

1. 8.1 Calculating Effect Sizes for Single Subject Designs

2. Classes of Effect Size Formulae Percentage of Non-Overlapping Data (PND) • Identify the lowest baseline point • Count the number of non-overlapping intervention points • Calculate the proportion of non-overlapping to total number of intervention points (can’t use if baseline has a zero point)

3. PND = 8/10 = 80%

4. Classes of Effect Size Formulae Standard Mean Difference • Subtract the mean of the baseline phase from the mean of the intervention phase • Divided by standard deviation of baseline

5. SMDall= 7.23 SMD3= 8.25

6. Classes of Effect Size Formulae Percentage Reduction (mean baseline reduction) • 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

7. MBR=339.00

8. Classes of Effect Size Formulae Regression Models • Regression equation obtained for baseline • Regression equation obtained for Tx data • Tx substracted from baseline and divided by standard deviation of baseline

9. Olive & Smith, 2005