Questions
 In a correlation research paper do the authors note
the predictive variable and the criterion variable?
 Is it common to combine different research
strategies in a single experiment?
 Do researchers sometimes make larger scales for
rating scale questions to produce a larger range of
responses in order to attempt to avoid the scale
being reduced?
 Does the type of survey determine what type of
question to ask, or is one question better to use
than another?
More Questions
 How valid are correlational studies when
there is always a directionality and thirdvariable problem that can affect the results?
 In what sub-field(s) of psychology are case
study designs most likely to be used?
 For the exercises from Ch11 on factorial
designs, I was confused on how to look at a
chart/table or a graph and see if there is an
interaction. Problems #8 and #9 were very
confusing for me.
Exam concepts
Experiment, third-variable problem,
directionality problem, manipulation and
control of variables, treatment conditions,
levels, ways of controlling extraneous
variables (holding constant, matching and
randomization), experimental and control
groups (no-treatment, placebo), simulation
and field studies
Exam concepts
 between-subjects design (what it is, major
adv and disadv), at least two examples of
threats to internal validity of btw-subjects
designs
 Within-subjects designs (what it is, major
adv and disadv - time-related, order),
dealing with time-related threads and order
effects, matched-subjects designs
(controlling time and counterbalancing)
Exam concepts
 Distinction btw nonexperimental and quasiexperimental research strategy,
nonequivalent group (general understanding
and one example of design), pre-post
designs (general understanding and one
example of design), developmental research
designs (cross-sectional and longitudinal –
differences), cohort effects
Exam concepts
 Factor, factorial design, main effect, interaction,
between and within-subjects factorial designs
(calculating number of participants and
deciphering the notation e.g. 2x3x2), mixed
designs
 Types of designs under descriptive research
strategy (observational, survey, case study), types
of observation, types of questions, correlation,
positive and negative correlation, predictor and
criterion variable, applications of correlations and
problems
Exam concepts
 Differences between case study and singlecase design, baseline phase, treatment
phase, visual inspection of data, provide
example of one specific type of a singlesubject design (e.g. ABAB), general adv and
disadv of single-subject designs
Single-Subject Research Designs
Chapter 13
Dusana Rybarova
Psyc 290B
June 1 2006
Outline:
1.
2.
3.
4.
5.
6.
Introduction to single-subject designs
Phases and phase changes
The ABAB reversal design
Dismantling or component-analysis design
Multiple-baseline designs
Strengths and weaknesses of singlesubject designs
1. Introduction to single-subject
designs
 single-subject designs or single-case design are
research designs that use the results from single
participant or subject to establish the existence of
cause-and-effect relationships
 Whereas case studies belong to the group of
descriptive research strategies, single-case
studies are experimental
 like time-series research, the single-subject
approach typically involves a series of
observations made over time but again singlesubject designs are experimental and time-series
designs are quasi-experimental
1. Introduction to single-subject
designs
 Evaluating the results from a single-subject
study
– the presentation and interpretation of results
form a single-subject experiment are based on
a simple graph of the data
– because the results of a single-subject study do
not involve any traditional statistical methods,
researchers must rely on the visual inspection
of a graph to convey the meaning of their
results
2. Phases and phase changes
 a phase is a series of observations of the same
individual under the same conditions
 when no treatment is being administered, the
observations are called baseline observations; a
series of baseline observations is called a baseline
phase and is identified by the letter A
 when a treatment is being administered, the
observations are called treatment observations. A
series of treatment observations is called a
treatment phase and is identified by the letter B.
2. Phases and phase changes
 a consistent level occurs when series of
measurements are all approximately the same
magnitude; in a graph, the series of data points
cluster around a horizontal line
 a consistent trend occurs when the differences
from one measurement to the next are
consistently in the same direction and are
approximantely of the same magnitude; in a graph
the series of the data points cluster around a
sloping line
2. Phases and phase changes
 the stability of a set of observations refers to
the degree to which the observations show
a pattern of consistent level or consistent
trend; stable data may show minor
variations from a perfectly consistent
pattern, but the variations should be
relatively small and the linear pattern
relatively clear
3. The ABAB reversal design
 An ABAB design, also known as a reversal
design, is a single-subject phase-change
design consisting of four phases: a baseline
phase, a treatment phase, a return to
baseline phase, and a second treatment
phase
 The goal of the design is to demonstrate
that the treatment causes changes in the
participant’s behavior
3. The ABAB reversal design
 Limitations of the ABAB design
– It is not appropriate for evaluating treatments
that are expected to have a permanent or longlasting effect
– There is also the ethical question of withdrawing
a successful treatment
4. Dismantling or componentanalysis design
 This design consists of a series of phases in which
each phase adds or subtracts one component of a
complex treatment to determine how each
component contributes to the overall treatment
effectiveness
 E.g. reward and punishment for biting behavior in
an autistic boy
BC-B-BC-C-BC
BC – combination of the reward and punishment
B – reward only
C – punishment only
5. Multiple-baseline designs
 When initial
baseline phases
correspond to
separate
participants, the
design is called
a multiplebaseline across
subjects
 Example (left)
from Walker,
Shippen,
Alberto,
Houchins and
Cihak (2005)
5. Multiple-baseline designs
 Advantages
– The major advantage of this design is that it eliminates
the need for a reversal or return-to-baseline phase and
is therefore well suited for evaluating treatment effects
that are permanent or long-lasting
 Disadvantages
– The results can be compromised by individual
differences between participants or between behaviors
(e.g. one participant being more responsive to the
treatment than another)
6. Strengths and weaknesses of
single-subject designs
 Advantages
– Researcher can establish a cause-and-effect relationship
between treatment and behavior using only a single
participant
– Flexibility – development of the design depends on
participant’s responses
 Disadvantages
– Problem with generalizations since designs use only one
participant
– Multiple observations can affect participant’s responses
– Absence of statistical controls and reliance on visual
inspection of the data
References
 Walker B., Shippen M.E., Alberto P.,
Houchins, D.E. & Cihak, D.F. (2005). Using
the Expressive Writing Program to Improve
the Writing Skills of High School Students
with Learning Disabilities. Learning
Disabilities Research and Practice, 20(3),
175-183.