Transcript Calculating Effect Sizes for Single Subject Designs

10.1
Calculating Effect Sizes
for
Single Subject Designs
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)
14
N
U
M
B
E
R
C
O
R
R
E
C
T
12
10
8
6
4
2
0
1
2
3
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6
7
8
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10
SESSIONS
PND = 8/10 = 80%
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15
Classes of Effect Size Formulae
Standard Mean Difference
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•
Subtract the mean of the baseline phase
from the mean of the intervention phase
Divided by standard deviation of baseline
14
N
U
M
B
E
R
C
O
R
R
E
C
T
12
10
8
6
4
2
0
1
2
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SESSIONS
SMDall= 7.23
SMD3= 8.25
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15
Classes of Effect Size Formulae
Percentage Reduction (mean baseline reduction)
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•
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
14
N
U
M
B
E
R
C
O
R
R
E
C
T
12
10
8
6
4
2
0
1
2
3
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6
7
8
9
SESSIONS
MBR=339.00
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Classes of Effect Size Formulae
Regression Models
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Regression equation obtained for baseline
Regression equation obtained for Tx data
Tx substracted from baseline and divided by
standard deviation of baseline
Olive & Smith, 2005