Single -Subject Designs - Ch 5
“Data collection allows teachers to
make statements about the direction
and magnitude of behavioral
changes” (p. 116).
In short, teachers can verify that their
instruction/intervention is working
based on data.
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Big Idea: An array of ABA
designs exists



Certain ABA designs (a.k.a. formats) can indicate
experimentally to others ‘what is working’ in your
classroom for your students.
Of all 6 designs, 3 do yield functional relationships
(ABAB, Changing Criterion, and Multiple Baseline)
Of all 6 designs, 3 do not yield functional relationships
(AB, Changing Conditions, and Alternating Treatment)


See glossary - p.425 for definition of functional relationship
See page 118 (‘Single-subject experimental designs
allow…cause of the effects’) for explanation of functional
relationships.
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Preface: The social sciences use two methods to
test hypotheses.
1.
2.
Group designs compare the performance of one
sample of individuals (e.g., people who don’t smoke,
or rabbits who don’t have smoke blown into their
cages) with another (e.g., people who do smoke, or
rabbits who do have smoke blown into their cages).
Single-subject designs compare the performance of an
individual* before and after a specified intervention.


Read pages 119-20 (‘Applied behavior analysis...they will
work.’)
*Note: Sometimes single-subject design procedures are
applied to groups (e.g., designated driver or graffiti studies).
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ABA - Baseline Requirements
“Baseline data are measures of the level of behavior (the dependent variable)
as it occurs naturally, before intervention.”



In order to evaluate whether your instruction is
achieving changes in your students’ school life, you
should begin with a baseline.
Baseline data are measures of the level of behavior
(recall the description of dependent variables) as it
occurs naturally (prior to your intervention).
Certain rules govern the collection of valid baeline data.
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ABA - Baseline Rules

General Assumption: Baseline will have at least 5
data points.

Stability of the baseline must be demonstrated
1.
2.
Stability is based on whether the baseline data represent the
group or vary a lot – highs and lows but no real average
group. Stability has also been called “variability.”
How the baseline data are trended - ascending or descending
- is also important.
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ABA - Baseline Requirements
When baselines are unstable (variable), the first
thing to examine is the definition of the target
behavior. A lack of stability in the baseline may
suggest the operational definition of the target
behavior is not sufficiently descriptive to allow
for accurate and consistent recording or that the
data collector is not being consistent in the
procedure used for data collection (p. 120).
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ABA - Baseline Requirements
Stability is based on whether the data vary a lot. This
has been termed “variability” and “stability.”
Example: # correct (16, 5, 9, 11, 10, 9)
A.
Find the mean (average) 60/6 = 10
B.
Divide the mean in half = 5
C.
Add & subtract B from the mean
= 5 and 15
D.
Determine if all baseline data fall
between the high & low range in C.
No.
Words Correct
Here’s how you determine this facet of baseline stability.
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ABA - Baseline Requirements
Examples:
If this chart is a picture of # correct on a
spelling test, we can say that the data are
appropriately trended. That is they are
going in the opposite direction of what we
seek - increasing spelling performance.
If this chart is a picture of # tattles on the
playground, we can say that the data are
not appropriately trended. That is, they
are going in the direction of what we seek
- decreasing tattling.
Words Correct
Stability is also based on how the data are trended ascending or descending. “…3 successive data points
in the same direction” (p. 121).
AT5.ppt
ABA - Baseline Requirements
Examples:
If this chart is a picture of # correct on a
spelling test, we can say that the data are
appropriately trended. That is they are
going in the opposite direction of what we
seek - increasing spelling performance.
If this chart is a picture of # tattles on the
playground, we can say that the data are
not appropriately trended. That is, they
are going in the direction of what we seek
- decreasing tattling.
Tattling Events
Stability is also based on how the data are trended ascending or descending. “…3 successive data points
in the same direction” (p. 121).
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Single Subject Designs
AB (a.k.a. “teacher”) Design
Some Considerations



Simplicity
Cannot be used to establish functional
relationship
Very vulnerable to confounding variables or
coincidental events
• See example on next slide.
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Single Subject Designs
1.AB (a.k.a. “teacher”) Design
Example: Spelling test performance for Jo-Jo
25
A
Words Correct
Note: Teacher
cannot confirm
that
intervention
produced the
successful
results.
B
20
15
10
5
0
1
2
3
4
5
6
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7
8
9
10
11
12
13
14
15
Single Subject Designs
2.ABAB (a.k.a. “reversal”) Design

Some Considerations






+Simplicity
+Functional relationship is established
-Takes longer
-Necessity of withdrawing an effective intervention
-Not appropriate with dangerous behaviors
Could appear as a BAB if behavior did not intitially
exist in subject’s repertoire
• See example on next slide.
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Single Subject Designs
ABAB (a.k.a. “reversal”) Design
Example: Spelling test performance for Jo-Jo
25
A
B
A
B
20
Words Correct
Note: Teacher
can confirm
that
intervention
produced the
successful
results.
15
10
5
0
1
3
5
7
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9
11 13 15 17 19 21 23 25 27 29 31
Single Subject Designs
3.Changing Criterion Design

Some Considerations
+Gradual acquisition may not be appropriate here
 +Functional relationship is established (w. 3 successful phases)
 +Continually progresses toward target behavior - no reversal
 +Appropriate in ‘shaping’ behaviors
 Requires setting interim and final goals
“After the student has reached the established level of performance in a
predetermined number of consecutive sessions (usually 2, or in 2 out
of three consecutive sessions of a subphase), the level of
performance required for reinforcement should be adjusted in the
direction of the desired level…Each successive interim level of
performance should be determined using the same mathematical
difference established at the first interim level of performance” (p.
131).
OYO Read 4 strategies on page 131.
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
Single Subject Designs
Changing Criterion Design
Example: Spelling test performance for Jo-Jo
25
B1
A
20
#correct / 20
Note: Teacher
can confirm
that
intervention
produced the
successful
results (w. 3
successful
phases).
B2
B3
15
10
5
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
Treatment Sessions
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Single Subject Designs
4.Multiple Baseline Design

Some Considerations



+Functional relationship is established w/o withdrawing
intervention - this is based on continuous data collection
of baseline
-Not appropriate when intervention is needed
immediately
Subsequent interventions are based on
• 3 data points trended appropriately
• Predetermined criteria (e.g., 4 of 5 appropriately trended points)

Second, third, etc. introductions of the intervention
yielding results constitutes replication
• See example on next slide.
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Single Subject Designs
Multiple Baseline Design
Example: Spelling test performance for Jo-Jo & D-D
B
A
18
16
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8
9
10
11
12
S essions
20
A
18
16
Number Correct
Note: Teacher
can confirm
that
intervention
produced the
successful
results
Number Correct
14
B
14
12
10
8
6
4
2
0
1
2
3
4
5
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6
7
8
9
S essions
10
11
12
13
14
15
Single Subject Designs
5.Alternating Treatment Design
(a.k.a. multiple schedule, alternating conditions, multiple element)

Some Considerations
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To fairly compare 2 (or more) interventions, counterbalance
administrations
Specify which intervention you are implementing “Now we are going
to use the CAI, not the TDI intervention
Applying the more effective intervention to the content can affirm that
the more effective intervention works better
Extending the effective intervention into an ABAB study can produce
a functional relationship
Allows teachers to make decisions about “what works” in classrooms
Use Wilson et. al (1996) example on p. 111 for further explanation.
• See example on next slide.
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Single Subject Designs
Alternating Treatment Design
Example: Spelling test performance for Jo-Jo
Teacher Presented
Note: Teacher
cannot confirm
that an
intervention
produced the
successful
results.
A
B
Computer Presented
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Single Subject Designs
6.Changing Conditions Design
(a.k.a. ABC)

Some Considerations




Used to compare 2 (or more) interventions
+Helpful in deciding what will work for a specific student after
Functional Behavioral Analysis
-No functional relationship occurs as a result
May include a return to baseline between each condition
(AB AC AD)
• See example on next slide.
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Single Subject Designs
Changing Conditions Design
Example: Spelling test performance for Jo-Jo
18
A
16
14
Number Correct
Note: Teacher
cannot confirm
that an
intervention
produced the
successful
results.
B
C
Earns Candy
12
10
8
Earns Money
6
4
2
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17
Sessions
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How are results evaluated?



Successfully repeating the intervention with a
subject adds credibility
Changes that produce “meaningful” results are
valued
Visually inspecting the data provides the best
evidence of effectiveness



Change in means
Levels of performance
Trends in performance
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How are results evaluated?
Change in means - difference between
baseline mean and intervention mean(s):
18
Baseline mean = 8.16
16
14
Number Correct

Intervention mean =
13.5
12
10
Change in means = 5.34
8
6
4
2
0
1
2
3
4
5
6
7
8
9
10
Sessions
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11
12
13.50
-8.16
5.34
How are results evaluated?
Level of performance - difference
between last baseline data point and first
intervention data point:
Last baseline data point
=5
18
16
First intervention data
point = 12
14
Number Correct

12
10
8
Level of performance
difference = +7
6
4
2
0
1
2
3
4
5
6
7
8
9
10
Sessions
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11
12
How are results evaluated?

18
Trend in performance - focuses on systematic
and consistent increases or decreases in
intervention performance
Average of first half of
intervention data points
= 13
16
Number Correct
14
12
Average of second half
of intervention data
points = 14.3
10
8
6
4
2
0
1
2
3
4
5
6
7
Sessions
8
9
10
11
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12
Connect the points and
determine if line
ascends, descends,
remains unchanged.