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Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Correlated-Groups Correlated-Groups and Single-Subject and Single-Subject DesignsDesignsGraziano and RaulinGraziano and RaulinResearch Methods: Chapter 11Research Methods: Chapter 11This multimedia product and its contents are protected under copyright law. The following are This multimedia product and its contents are protected under copyright law. The following are prohibited by law: (1) Any public performance or display, including transmission of any image prohibited by law: (1) Any public performance or display, including transmission of any image over a network; (2) Preparation of any derivative work, including the extraction, in whole or in over a network; (2) Preparation of any derivative work, including the extraction, in whole or in part, of any images; (3) Any rental, lease, or lending of the program.part, of any images; (3) Any rental, lease, or lending of the program.
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Correlated-Groups Correlated-Groups DesignsDesigns Introduces a correlation between Introduces a correlation between
groups in the way groups are groups in the way groups are formedformed– Within-subjects design:Within-subjects design:
Same participants in each groupSame participants in each group
– Matched-groups designMatched-groups design Uses matched random assignmentUses matched random assignment
More sensitive than independent-More sensitive than independent-groups designsgroups designs
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Within-Subjects Within-Subjects DesignsDesigns All participants are exposed to all All participants are exposed to all
experimental conditionsexperimental conditions Need to control for sequence Need to control for sequence
effectseffects– The experience with one condition The experience with one condition
affecting performance in subsequent affecting performance in subsequent conditionsconditions
– Controlled by varying the order of Controlled by varying the order of presentation (counterbalancing)presentation (counterbalancing)
Sequence EffectsSequence Effects
SOURCESSOURCES– Positive Practice Positive Practice
Effects (PPE)Effects (PPE)– Negative Practice Negative Practice
Effects (NPE)Effects (NPE)– Carryover EffectsCarryover Effects
CONTROLSCONTROLS– Control PPE with Control PPE with
prior trainingprior training– Control NPE with Control NPE with
rest intervalsrest intervals– Control carryover Control carryover
effects by varying effects by varying the order of the order of conditionsconditions
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Target Search StudyTarget Search Study
Hypothetical StudyHypothetical Study– Within-subjects designWithin-subjects design– Six participants; order counterbalancedSix participants; order counterbalanced– Three conditionsThree conditions
10 distracters10 distracters 15 distracters15 distracters 20 distracters20 distracters
Design on next slideDesign on next slide Data on the following slideData on the following slide
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Within-SubjectsWithin-SubjectsDesign ExampleDesign Example
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Target Search StudyTarget Search Study
ConditionsConditions
AA(10)(10)
BB(15)(15)
CC(20)(20)ParticipaParticipa
ntntOrderOrder
11 ABCABC 18.3318.33 22.3922.39 24.9724.97
22 ACBACB 15.9615.96 20.7220.72 21.7921.79
33 BACBAC 19.0219.02 22.7822.78 25.4625.46
44 BCABCA 25.3625.36 27.4827.48 27.9127.91
55 CABCAB 19.5219.52 24.6424.64 26.7526.75
66 CBACBA 23.2723.27 24.9624.96 25.4925.49
Mean ScoresMean Scores 20.2420.24 23.8323.83 25.4025.40
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Graph of ResultsGraph of Results
The graph shows The graph shows how the mean how the mean search time search time increases as the increases as the number of number of distracter items distracter items increasesincreases 0
5
10
15
20
25
30
Search
Time
10 15 20
Number of Distracters
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Statistical AnalysisStatistical Analysis
Appropriate Statistical AnalysesAppropriate Statistical Analyses– Correlated Correlated tt-test (for 2 groups only)-test (for 2 groups only)
– Repeated measures ANOVARepeated measures ANOVA Order data so that each line Order data so that each line
represents one participant and represents one participant and each column represents one each column represents one conditioncondition– Note that the columns represent conditions, Note that the columns represent conditions,
NOT the order of testingNOT the order of testing
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
ANOVA Summary TableANOVA Summary Table
SourceSource dfdf SSSS MSMS FF pp
BetweenBetween 22 83.6983.69 41.8541.85 32.2532.25 <0.01<0.01
SubjectsSubjects 55 95.8595.85 19.1719.17
ErrorError 1010 12.9712.97 1.301.30
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Within-Subjects Within-Subjects StrengthsStrengths More sensitive to small group More sensitive to small group
differencesdifferences – The variability due to individual The variability due to individual
differences is statistically eliminateddifferences is statistically eliminated Fewer participants are neededFewer participants are needed
– Each participant appears in each conditionEach participant appears in each condition Instructions may take less timeInstructions may take less time
– Participants were already instructed on the Participants were already instructed on the task in previous conditionstask in previous conditions
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Within-Subjects Within-Subjects WeaknessesWeaknesses Because participants experience all Because participants experience all
conditions, they may figure out the conditions, they may figure out the hypothesis (potential subject effects)hypothesis (potential subject effects)
Major issue is sequence effectsMajor issue is sequence effects– Practice and carry-over effectsPractice and carry-over effects– Controlled by varying the order of Controlled by varying the order of
presentationpresentation CounterbalancingCounterbalancing Random order of presentationRandom order of presentation Latin square designLatin square design
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Matched-Subjects Matched-Subjects DesignsDesigns Introduces correlation through Introduces correlation through
matched random assignmentmatched random assignment Should match on “relevant” Should match on “relevant”
variablesvariables– Variables that affect the dependent Variables that affect the dependent
variablevariable– Variables that show considerable Variables that show considerable
natural variation in the population natural variation in the population sampledsampled
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Matching ParticipantsMatching Participants
Match participants in setsMatch participants in sets– Set size is equal to the number of conditionsSet size is equal to the number of conditions
Matching gets more difficult as:Matching gets more difficult as:– The number of matching variables increasesThe number of matching variables increases– Matching is done on continuous variablesMatching is done on continuous variables– The number of conditions increaseThe number of conditions increase
Once sets are matched, randomly assign Once sets are matched, randomly assign participants in the set to the conditionsparticipants in the set to the conditions
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Statistical AnalysisStatistical Analysis
Analyze as if it were a within-subjects Analyze as if it were a within-subjects studystudy– Data from matched participants are organized Data from matched participants are organized
as if the data came from a single participantas if the data came from a single participant Act as if the number of participants was Act as if the number of participants was
equal to the actual number of participants equal to the actual number of participants divided by the number of conditionsdivided by the number of conditions(e.g., for 40 participants and 4 conditions, tell the program (e.g., for 40 participants and 4 conditions, tell the program that you had 10 participants and 4 conditions in a within-that you had 10 participants and 4 conditions in a within-subjects design)subjects design)
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Strengths and Strengths and WeaknessesWeaknesses StrengthsStrengths
– Increased sensitivity to group Increased sensitivity to group differencesdifferences
– No sequence effects No sequence effects WeaknessesWeaknesses
– Extra work of matching participantsExtra work of matching participants– Participants without appropriate Participants without appropriate
matches cannot be used in the studymatches cannot be used in the study
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Single-Subject DesignsSingle-Subject Designs
Extensions of within-subjects designsExtensions of within-subjects designs Single participant tested under all Single participant tested under all
conditions, with the researcher conditions, with the researcher actively manipulating the actively manipulating the independent variableindependent variable
Variation on time-series designs, with Variation on time-series designs, with repeated measurement of the repeated measurement of the dependent variabledependent variable
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
History of these History of these DesignsDesigns Intensive studies of individuals Intensive studies of individuals
was common before R. A. Fisherwas common before R. A. Fisher Fisher’s development of ANOVA Fisher’s development of ANOVA
changed the focus of psychology changed the focus of psychology to comparing groups of to comparing groups of individualsindividuals
Skinner was one of the few Skinner was one of the few psychologists who advocated the psychologists who advocated the intensive study of individualsintensive study of individuals
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Logic of these DesignsLogic of these Designs
Includes independent variable Includes independent variable manipulationmanipulation
Expect dependent variable responseExpect dependent variable response– Note that the response must occur shortly Note that the response must occur shortly
after the manipulation unless there is a after the manipulation unless there is a theoretical reason to expect a delaytheoretical reason to expect a delay
Multiple measures before and after the Multiple measures before and after the manipulation to identify normal variation manipulation to identify normal variation and rule out regression to the meanand rule out regression to the mean
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Single-Subject DesignsSingle-Subject Designs
Basic Single-Subject design includesBasic Single-Subject design includes– Baseline periodBaseline period– A treatment phaseA treatment phase– A post-treatment evaluation periodA post-treatment evaluation period
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Types of DesignsTypes of Designs
ABA Reversal DesignABA Reversal Design Multiple Baseline DesignMultiple Baseline Design Single-Subject, Randomized, Single-Subject, Randomized,
Time-Series DesignTime-Series Design
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Reversal DesignReversal Design
LOGICLOGIC– Apply, then Apply, then
remove, remove, independent independent variable variable manipulationmanipulation
– If change occurs at If change occurs at both application both application and removal, it and removal, it suggests a causal suggests a causal connectionconnection
PROCEDURESPROCEDURES– Baseline measures Baseline measures
(Condition A)(Condition A)– Treatment Treatment
application application (Condition B)(Condition B)
– Return to baseline Return to baseline (Condition A again)(Condition A again)
– Additional Additional reversals can be reversals can be includedincluded
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Reversal Design Reversal Design Example Example Reversal conditionsReversal conditions
– Condition A: attending to self-Condition A: attending to self-stimulation stimulation
– Condition B: withdrawing attention Condition B: withdrawing attention when self-stimulation occurswhen self-stimulation occurs
Hypothetical results (next slide) Hypothetical results (next slide) suggests that attention does suggests that attention does influence self-stimulationinfluence self-stimulation
Ethics requires return to Condition BEthics requires return to Condition B
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Published Example Published Example DeLeon et al. (1997)DeLeon et al. (1997)
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Multiple Baseline Multiple Baseline DesignDesign LOGICLOGIC
– Show the effect of Show the effect of the independent the independent variable on several variable on several dependent dependent variablesvariables
– Use when Use when Reversals are Reversals are
undesirableundesirable Behavioral changes Behavioral changes
would not reversewould not reverse
PROCEDURESPROCEDURES– BaselineBaseline– Manipulation Manipulation
focused on first focused on first dependent variabledependent variable
– Manipulation Manipulation focused on second focused on second dependent variabledependent variable
– ……and so onand so on
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Multiple Baseline Multiple Baseline DesignDesign
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Variations onVariations onMultiple Baseline Multiple Baseline DesignDesign Across BehaviorsAcross Behaviors
– Testing effects on different Testing effects on different behaviorsbehaviors
Across IndividualsAcross Individuals– Testing effects on different peopleTesting effects on different people
Across Settings and TimeAcross Settings and Time– Testing effects in different settings Testing effects in different settings
or at different timesor at different times
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Single-Subject, Single-Subject, Randomized Time-Series Randomized Time-Series DesignDesign LOGICLOGIC
– Repeated Repeated measures of the measures of the dependent variable dependent variable interrupted by a interrupted by a randomly placed randomly placed interventionintervention
– If change occurs at If change occurs at the point of the point of intervention, it intervention, it suggests a causal suggests a causal connectionconnection
PROCEDURESPROCEDURES– Select minimum Select minimum
baseline and baseline and follow-up periodsfollow-up periods
– Randomly select Randomly select the point of the point of interventionintervention
– Compare pattern Compare pattern of scores before of scores before and after the and after the interventionintervention
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Single-Subject, Single-Subject, Randomized Time-Series Randomized Time-Series DesignDesign
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Replicating Single-Replicating Single-Subject ExperimentsSubject Experiments Direct replicationDirect replication
– Repeating study on the same target Repeating study on the same target behavior behavior
Systematic replicationSystematic replication– Evaluate procedures across subjects, Evaluate procedures across subjects,
settings, and/or target behaviorssettings, and/or target behaviors Clinical replicationClinical replication
– Combining procedures into a treatment Combining procedures into a treatment “package”“package”
Ethical PrinciplesEthical Principles
Ethics in treatment studiesEthics in treatment studies– First, do no harmFirst, do no harm– Second, try to do some goodSecond, try to do some good
ThereforeTherefore– Researcher is ethically bound to leave Researcher is ethically bound to leave
participants in the best situation, participants in the best situation, which often means returning to which often means returning to treatment in the reversal designtreatment in the reversal design
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)
SummarySummary
Can introduce a correlation in two waysCan introduce a correlation in two ways– Within-subjects and matched-subjects Within-subjects and matched-subjects
designsdesigns These designs are more sensitive to small These designs are more sensitive to small
differences between groupsdifferences between groups The costs for the greater sensitivity are:The costs for the greater sensitivity are:
– Sequence effects (within-subjects design) Sequence effects (within-subjects design) – Matching difficulties (matched-subjects Matching difficulties (matched-subjects
design)design) Single-subject designs allow the Single-subject designs allow the
experimental manipulation of variablesexperimental manipulation of variables