Lecture 18: Single-Subject Designs

Question 1

how do we statistically analyze between-subjects designs?

Answer 1

an independent subjects t-test or between-subjects ANOVA

Question 2

how do we statistically analyze within-subjects designs?

Answer 2

a dependent subjects t-test or repeated measures ANOVA

Question 3

Single-subject (single-case) designs

Answer 3

research designs that use the results from a single participant or subject

Question 4

goal of single-subject designs

Answer 4

Establish the existence of cause-and-effect relationships

Question 5

how are single-case experimental designs conducted

Answer 5

by manipulating an IV and controlling extraneous variables to prevent alternative explanations for the research results

Question 6

alternative explanations for research results in a single-subject design

Answer 6

• Baseline
• Repeated observations
• Replication

Question 7

evaluating results from a single-case study

Answer 7

• Data are evaluated in a simple graph because statistical tests for significance cannot be used
• Contrary to what is stated in the textbook, several statistical significance tests could be used to compare the level and trend between the A and B phases
• However, such a graph by itself is not enough to show that the treatment caused a behavioural change

Question 8

why are graphs not enough to show that the treament caused a behavioural change?

Answer 8

• No control over extraneous variables
• This could be the result of chance

Question 9

phase

Answer 9

series of observations of the same individual under the same conditions

Question 10

when are baseline observations made?

Answer 10

when no treatment is being administered

Question 11

baseline phase

Answer 11

a series of baseline observations

Question 12

baseline notation

Answer 12

Identified by the letter A

Question 13

treatment observations

Answer 13

observations made when a treatment is being administered

Question 14

treatment phase

Answer 14

a series of treatment observations

Question 15

treatment notation

Answer 15

• Identified by the letter B
• Subsequent treatments are identified by subsequent letters (ex. c, d, e)

Question 16

function of baseline and treatment annotation

Answer 16

Allows researchers to describe the phases in a study by using a sequence of letters

Question 17

consistent level

Answer 17

• A series of measurements that are all nearly the same magnitude
• Graphed data points cluster around a horizontal line

Question 18

consistent trend

Answer 18

• Differences from one measurement to the next that are consistently in the same direction and nearly the same magnitude
• Graphed data points cluster around a sloping line

Question 19

stability

Answer 19

• 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
• Variations should be relatively small and the linear pattern relatively clear

Question 20

strategies for dealing with unstable data

Answer 20

• Wait until the data stabilize
• Average a set of two or more observations
• Look for patterns within the inconsistency

Question 21

length of a phase

Answer 21

• To establish a pattern (level or trend) within a phase and to determine the stability of the data within a phase, a phase must consist of a minimum of three observations
• Two observations, by themselves, do not provide enough information to determine a pattern.
• Additional observations beyond the first two are essential to establish level, trend, and stability.
• Typically, five or six observations are necessary to determine a clear pattern
• When high variability exists in the data points, additional observations should be made

Question 22

phase change

Answer 22

a manipulation of the independent variable

Question 23

what are accomplished with phase changes?

Answer 23

• Implementing a new treatment
• Withdrawing a treatment
• Changing a treatment

Question 24

function of changing phases

Answer 24

Initiates a new phase in which the researcher collects observations under new conditions

Question 25

when should we change phases?

Answer 25

When a clear pattern has emerged from the preceding phase

Question 26

what factors should we consider when assessing participants’ responses to phases?

Answer 26

• If they are improving without treatment, don’t implement the treatment.
• If they are deteriorating quickly, implement the treatment right away.
• If the treatment produces immediate and severe deterioration, cease or modify treatment immediately.

Question 27

visual inspection techniques

Answer 27

characteristics that help determine whether there is a meaningful change between phases

Question 28

examples of visual inspection techniques

Answer 28

• Change in the average level
• Immediate change in level
• Change in trend
• Latency of change

Question 29

tools to enhance visual inspection techniques

Answer 29

• Use lines representing a level in each phase and a band representing +/- 2 standard deviations
• Use lines representing the trend in each phase

Question 30

phases of an ABAB design

Answer 30

A baseline phase (A), followed by treatment (B), then a return to baseline (A), and finally a repetition of the treatment phase (B)

Question 31

goal of an ABAB design

Answer 31

to demonstrate that the treatment causes changes in the participant’s behaviour

Question 32

demonstrating that the ABAB design causes a change in behaviour

Answer 32

• The pattern of behaviour in each treatment phase (different from the pattern in each baseline phase)
• The changes in behaviour from baseline to treatment and from treatment to baseline (the same for each of the phase-change points in the experiment)

Question 33

limitations of the ABAB design

Answer 33

• Withdrawal from treatment
• This may not result in a change in behaviour (the patient is cured)
• This may result in a slight change but not a return to the baseline
• This may cause an ethical problem if the treatment is working for the participant

Question 34

variations on the ABAB design

Answer 34

• Sometimes researchers add a treatment or modify the sequence of baseline and treatment phases.
• Creates a complex design
• Researchers must incorporate new treatments into the phase sequence to prove a causal relationship.
• ABBCAC, ABCBC, etc.

Question 35

multiple baseline design

Answer 35

• The treatment phase is initiated for one baseline
• Baseline observations continue for the other
• The treatment is initiated for the second baseline at a different time

Question 36

multiple-baseline across subjects

Answer 36

the initial baseline phases correspond to the same behaviour for two separate participants

Question 37

multiple-baseline across behaviours

Answer 37

the initial baseline phases correspond to two separate behaviours for the same participant

Question 38

multiple-baseline across situations

Answer 38

the initial baseline phases correspond to the same behaviour in two separate situations

Question 39

component analysis designs

Answer 39

• Each phase adds or subtracts one component of a complex treatment
• Determines how each component contributes to the overall treatment effectiveness
• Component analysis with a reversal design
• Component analysis with a multiple-baseline design

Question 40

rationale for multiple-baseline designs

Answer 40

• The criteria for a successful multiple-baseline experiment are essentially identical to the criteria described earlier to define the success of an ABAB design
• There is a clear and immediate change in the pattern of behaviour when the researcher switches from a baseline to a treatment phase
• The design includes at least two demonstrations that behaviour changes when the treatment is introduced
• This replication is necessary to establish a causal relationship between treatment and behaviour

Question 41

strength of a multiple-baseline design

Answer 41

• No return to baseline needed
• Good for long-lasting treatments

Question 42

weaknesses of a multiple-baseline design

Answer 42

• It can be difficult to identify similar but independent behaviours
• Results can be compromised by individual differences between participants or between behaviours

Question 43

strengths of single-case designs

Answer 43

• Allows researchers to establish cause-and-effect relationships with one participant or subject
• Flexibility: the researcher is free to modify the treatment or change to a new treatment if a participant or subject fails to respond to the treatment
• No need to standardize treatment across groups—a single participant or subject is used

Question 44

weakenesses of single-case designs

Answer 44

• Relationship among variables is for only one participant or subject
• May threaten external validity (generalization)
• Multiple, continuous observations are required
• Absence of statistical controls
• Reliance on graphs to display data
• Treatment effects must be large and immediate to produce a convincing graph