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Chapter 7
ClarifyingResearch
Designs
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Quantitative Research
DescriptiveDescriptive
CorrelationalCorrelational
Quasi-experimentalQuasi-experimental
ExperimentalExperimental
IncreasedIncreased
ControlControl
withwithDesignDesign
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Research Design
Definition: Blueprint or detailedDefinition: Blueprint or detailed
plan for conducting a studyplan for conducting a study
Purpose, Review of Literature, &Purpose, Review of Literature, &
FrameworkFramework
Study DesignStudy Design
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Concepts Relevant to Design
Causality:Causality: AA BB
PressurePressure UlcerUlcer Multicausality:Multicausality:
Years SmokingYears Smoking
High-Fat DietHigh-Fat Diet
Limited ExerciseLimited Exercise
HeartDisease
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Concepts Relevant to Design
ProbabilityProbability:: likelihood oflikelihood of
accurately predicting an eventaccurately predicting an event BiasBias:: slanting findings awayslanting findings away
from the truthfrom the truth
ManipulationManipulation:: implementationimplementationof a treatmentof a treatment
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Concepts Relevant to Design
ControlControl
Implemented throughout the designImplemented throughout the design Improve accuracy of findingsImprove accuracy of findings
Increased control in quasi-Increased control in quasi-experimental researchexperimental research
Greatest in experimental researchGreatest in experimental research
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Varying Control in Studies
Quasi-experimentalQuasi-experimental ExperimentalExperimental
Lower ControlLower Control High ControlHigh Control
Type of Sample Selected:Type of Sample Selected:
Convenience ----------|--------> RandomConvenience ----------|--------> Random
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Varying Control in Studies
Quasi-experimentalQuasi-experimental ExperimentalExperimental
Lower ControlLower Control High ControlHigh Control
Type of Sample Selected:Type of Sample Selected:
Heterogeneous -----|----> HomogeneousHeterogeneous -----|----> Homogeneous
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Varying Control in Studies
MeasurementMeasurement
of Dependent Variableof Dependent Variable
CrudeCrude PrecisePrecise
Measurement------|----> MeasurementMeasurement------|----> Measurement
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Varying Control in Studies
ControlControl
of Independent Variableof Independent Variable
Limited orLimited or HighlyHighly
no Control ----------|--------> Controlledno Control ----------|--------> Controlled
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Varying Control in Studies
Quasi-experimentalQuasi-experimental ExperimentalExperimental
Lower ControlLower Control High ControlHigh Control
GroupGroup
no comparison group ----> comparisonno comparison group ----> comparison
group ----> alternative treatmentgroup ----> alternative treatmentcontrol group ----> no treatment controlcontrol group ----> no treatment control
groupgroup
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Varying Control in Studies
Selection of GroupsSelection of Groups
No randomization ---------> RandomizationNo randomization ---------> Randomization
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Varying Control in Studies
Quasi-experimentalQuasi-experimental ExperimentalExperimental
Lower ControlLower Control High ControlHigh Control
Setting SelectedSetting Selected
HighlyHighly
Natural -----------|----------> ControlledNatural -----------|----------> Controlled
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Design Validity
Measure of truth or accuracy of aMeasure of truth or accuracy of a
study examined with critique &study examined with critique &
controlled in conducting a studycontrolled in conducting a study
Statistical conclusion validityStatistical conclusion validity
Internal validityInternal validity
Construct validityConstruct validity
External validityExternal validity
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Types of Design Validity
Statistical Conclusion ValidityStatistical Conclusion Validity ----
is concerned with whether theis concerned with whether theconclusions about relationships orconclusions about relationships or
differences drawn from statisticaldifferences drawn from statistical
analyses are an accurate reflectionanalyses are an accurate reflectionof the real world.of the real world.
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Statistical Conclusion Validity
Low statistical power: Type II error,Low statistical power: Type II error,
no significant difference whenno significant difference whenthere is.there is.
Violated assumptionsViolated assumptions
At least interval dataAt least interval data Random sampleRandom sample
Normal distributionNormal distribution
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Statistical Conclusion Validity
Reliability of Instruments:Reliability of Instruments:
consistency in measurementconsistency in measurement Physiological measures: Precision,Physiological measures: Precision,
such as with temp., BPsuch as with temp., BP
Likert scale: Homogeneity--ReliabilityLikert scale: Homogeneity--Reliability
with Cronbachs alpha (.7, .8, .9)with Cronbachs alpha (.7, .8, .9) Observations: Stability--InterraterObservations: Stability--Interrater
reliabilityreliability
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Internal Validity --Internal Validity --
is the extent to which the effectsis the extent to which the effectsdetected in the study are adetected in the study are a
true reflection of reality,true reflection of reality,
rather than the result ofrather than the result of
extraneous variablesextraneous variables..
Types of Design Validity
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Internal Validity
History: event impacting subjectsHistory: event impacting subjects
& data collected& data collected
Maturation of subjects: wiser, tired,Maturation of subjects: wiser, tired,
older influencing responsesolder influencing responses
Testing: learn from being in studyTesting: learn from being in study
Instruments accuracyInstruments accuracy
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Internal Validity
Subject selection nonrandomSubject selection nonrandom
& potentially biased& potentially biased
Mortality: those dropping outMortality: those dropping out
of studyof study
Diffusion or imitation of treatment:Diffusion or imitation of treatment:control or comparison groupcontrol or comparison group
has access to treatmenthas access to treatment
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Construct Validity
Validity of instrumentsValidity of instruments
Physiologic measure: AccuracyPhysiologic measure: Accuracy
Scales: construct validityScales: construct validity
Mono-operation bias: 1 instrumentMono-operation bias: 1 instrument
to measure a variableto measure a variable
Mono-method bias: 1 type ofMono-method bias: 1 type of
instrument, such as attitude scalesinstrument, such as attitude scales
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Construct Validity
Subjects guessing outcome of studySubjects guessing outcome of study
& acting in a different way& acting in a different way
Subjects performing for experimentSubjects performing for experiment
to be seen in a good light or trying toto be seen in a good light or trying to
get an effective treatmentget an effective treatment
Treatment interactions with moreTreatment interactions with more
than one treatmentthan one treatment
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External Validity---External Validity---
is concerned with the extent tois concerned with the extent towhich study findings can bewhich study findings can be
generalized beyond the samplegeneralized beyond the sample
used in the study.used in the study.
Types of Design Validity
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External Validity
Interactions of:Interactions of:
Selection of subjects & treatmentSelection of subjects & treatment Setting & treatment: closing clinic,Setting & treatment: closing clinic,
nonsupportive staffnonsupportive staff
History & treatment: eventsHistory & treatment: eventsinfluence treatmentinfluence treatment
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Elements of Strong Design
Controlling the Environment:Controlling the Environment:
selection of the study settingselection of the study setting Natural settingNatural setting
Partially controlled setting: clinicPartially controlled setting: clinic
Highly controlled setting: labHighly controlled setting: lab
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Elements of Strong Design
Controlling the Equivalence ofControlling the Equivalence of
Subjects & GroupsSubjects & Groups Random subjectRandom subject
selectionselection
Random assignmentRandom assignment
to groupsto groups
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Elements of Strong Design
Controlling the Treatment (Tx)Controlling the Treatment (Tx)
Tx based on research & practiceTx based on research & practice Protocol developed for implementationProtocol developed for implementation
Document Tx was implementedDocument Tx was implemented
Checklist to determine extent TxChecklist to determine extent Txwas implemented if incompletewas implemented if incomplete
Re-evaluate Tx during studyRe-evaluate Tx during study
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Elements of Strong Design
Controlling MeasurementControlling Measurement
ReliabilityReliability ValidityValidity
# Measurement methods# Measurement methods
Types of instrumentsTypes of instruments
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Elements of Strong Design
Controlling Extraneous VariablesControlling Extraneous Variables
Identify & eliminate by sampleIdentify & eliminate by sample
criteria, setting, designcriteria, setting, design
Random samplingRandom sampling
Sample: heterogeneous, homogeneous,Sample: heterogeneous, homogeneous,matchingmatching
Statistical controlStatistical control
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Problems with Study Designs
Inappropriate for purposeInappropriate for purpose
& framework& framework
Poorly developedPoorly developed
Poorly implementedPoorly implemented
Inadequate treatment, sample,Inadequate treatment, sample,
measurement methodsmeasurement methods
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Critiquing a Study Design
1.1. Was the type of design identified?Was the type of design identified?
2.2. Was the study design linked to theWas the study design linked to thepurpose &/or objectives, questions,purpose &/or objectives, questions,
or hypotheses?or hypotheses?
3.3. Were all variables manipulatedWere all variables manipulated
or measured?or measured?
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Critiquing a Study Design
4. If the study included a treatment, was it4. If the study included a treatment, was it
clearly described & consistentlyclearly described & consistently
implemented?implemented?5.5. Were extraneous variables identified &Were extraneous variables identified &
controlled?controlled?
6.6. What were the threats to design validity inWhat were the threats to design validity inthis study?this study?
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Critiquing a Study Design
7.7. Was a pilot study performed priorWas a pilot study performed prior
to this study? What was the reasonto this study? What was the reason
for the pilot & the outcome?for the pilot & the outcome?
* Study feasibility* Study feasibility
* Refine design or treatment* Refine design or treatment
* Examine validity & reliability* Examine validity & reliability
of measurement methodsof measurement methods
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Identifying a Design
in a Quantitative
Research Report
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Types of DesignsTypes of Designs
Descriptive Study DesignsDescriptive Study Designs
Correlational Study DesignsCorrelational Study Designs Quasi-ExperimentalQuasi-Experimental
Study DesignsStudy Designs Experimental Study DesignsExperimental Study Designs
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Identifying a DesignIdentifying a DesignIs there a treatment?Is there a treatment?
NoNo YesYes
Is the treatment tightly controlledIs the treatment tightly controlled
by the researcher?by the researcher?Is the primary purposeIs the primary purpose
examination of relationships?examination of relationships?
NoNo YesYes
CorrelationalCorrelational
DesignDesign
NoNo YesYes
ExperimentalExperimental
StudyStudy
NoNo YesYes
Quasi-ExperimentalQuasi-Experimental
StudyStudyWill a randomly assignedWill a randomly assigned
control group be usedcontrol group be used
NoNo YesYes
Is the original sampleIs the original sample
randomly selected?randomly selected?
Will the sample beWill the sample be
studied as a singlestudied as a single
group?group?
NoNo YesYes
DescriptiveDescriptive
DesignDesign
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Identifying a Descriptive DesignIdentifying a Descriptive Design
Examining sequences across time?Examining sequences across time?
NoNo
Cross-sectional designCross-sectional design
NoNo YesYes
ComparativeComparative
DescriptiveDescriptive
DesignDesign
One Group?One Group?
DescriptiveDescriptive
DesignDesign
YesYes
Following same subjects across time?Following same subjects across time?
Studying events partitionedStudying events partitioned
across time?across time?CaseCase
StudyStudy
NoNo YesYes
NoNo
Data collectedData collected
across timeacross time
YesYes
Single unitSingle unit
of studyof study
NoNo YesYes
LongitudinalLongitudinal
StudyStudy
Trend AnalysisTrend Analysis Repeated measures of each subjectRepeated measures of each subject
NoNo YesYes
YesYes NoNo
Cross-sectional designCross-sectional designwith treatment partitioningwith treatment partitioning
Longitudinal design withLongitudinal design withtreatment partitioningtreatment partitioning
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Descriptive Study Designs
Typical Descriptive DesignTypical Descriptive Design
Comparative Descriptive DesignComparative Descriptive Design
Time Dimensional DesignTime Dimensional Design
Case Study DesignCase Study Design
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Diagramming the Design
Clarifies the variables to beClarifies the variables to be
measured or manipulatedmeasured or manipulated
Indicates focus of the study:Indicates focus of the study:
description, relationships,description, relationships,
differences, &/or testing adifferences, &/or testing a
treatmenttreatment
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Diagramming the Design
Identifies data collection process:Identifies data collection process:
time for study, treatmenttime for study, treatment
implementation, measurementimplementation, measurement
of variablesof variables
Provides direction toProvides direction to
data analysisdata analysis
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Typical Descriptive Design
ClarificationClarification MeasurementMeasurement DescriptionDescription InterpretationInterpretation
PhenomenonPhenomenon
of Interestof Interest
DescriptionDescription
ofof
Variable 1Variable 1
DescriptionDescription
ofof
Variable 2Variable 2
DescriptionDescription
ofofVariable 3Variable 3
DescriptionDescription
ofof
Variable 4Variable 4
Variable 1Variable 1
Variable 2Variable 2
Variable 4Variable 4
Variable 3Variable 3
InterpretationInterpretation
of Meaningof Meaning
Development ofDevelopment of
HypothesesHypotheses
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Comparative Descriptive Design
Group IGroup I
{variable(s){variable(s)
measured}measured}
Group IIGroup II{variable(s){variable(s)
measured}measured}
DescribeDescribe
InterpretationInterpretation
of Meaningof Meaning
Comparison ofComparison of
Groups onGroups on
Selected VariablesSelected Variables
DescribeDescribe DevelopmentDevelopment
of Hypothesesof Hypotheses
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Correlational Study Designs
DescriptiveDescriptive
Correlational DesignCorrelational Design Predictive DesignPredictive Design
Model-Testing DesignModel-Testing Design
Identif ing T pe of
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Identifying Type of
Correlational Design
DescribeDescribe
relationshipsrelationships
between/amongbetween/among
variables?variables?
PredictPredict
relationshipsrelationships
between/amongbetween/among
variables?variables?
TestTest
theoreticallytheoretically
proposedproposed
relationships?relationships?
DescriptiveDescriptive
correlationalcorrelational
designdesign
PredictivePredictive
correlationalcorrelational
designdesign
ModelModel
testingtesting
designdesign
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Descriptive Correlational Design
ResearchResearch
VariableVariable
11
ResearchResearch
VariableVariable
22
DescriptionDescription
of variableof variable InterpretationInterpretation
of Meaningof Meaning
Examination ofExamination of
RelationshipRelationship
DescriptionDescription
of variableof variableDevelopmentDevelopment
of Hypothesesof Hypotheses
MeasurementMeasurement
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Predictive Design
ValueValue
ofof
InterceptIntercept
Value ofValue of
IndependentIndependent
VariableVariable
11
Value ofValue of
IndependentIndependent
VariableVariable
22
PredictedPredicted
Value ofValue of
DependentDependent
VariableVariable
++ ++ ==
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Study Groups
Groups in comparativeGroups in comparative
descriptive studiesdescriptive studies
Control groupControl group
Comparison groupComparison group
Equivalent versusEquivalent versus
nonequivalent groupsnonequivalent groups
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Pre-Experimental Designs
One-group post-testonly designOne-group post-testonly design
Post-testonly design withPost-testonly design withnonequivalent groupsnonequivalent groups
One-group pretestpost-testOne-group pretestpost-test
designdesign
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Quasi-Experimental Designs
Untreated control group designUntreated control group design
with pretest & post-testwith pretest & post-test
Nonequivalent dependentNonequivalent dependent
variables designvariables design
Removed-treatment designRemoved-treatment design
with pretest & post-testwith pretest & post-test
P t t P t T t C t l
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PretestPost-Test ControlGroup Design
MeasurementMeasurement
of dependentof dependent
variablesvariables
Manipulation ofManipulation of
independentindependent
variablevariable
MeasurementMeasurement
of dependentof dependent
variable(s)variable(s)
Randomly selectedRandomly selected
experimentalexperimentalgroupgroup
PRETESTPRETEST TREATMENTTREATMENT POST-TESTPOST-TEST
Randomly selectedRandomly selected
control groupcontrol group
Treatment:Treatment: Under control of researcherUnder control of researcher
Findings:Findings: comparison of pretest and post-test scorescomparison of pretest and post-test scores
comparison of experimental and control groupscomparison of experimental and control groups
comparison of pretest-post-test differences between samplescomparison of pretest-post-test differences between samples
Example:Example: Your self (1990). The impact of group reminiscence counseling on a depressed elderlyYour self (1990). The impact of group reminiscence counseling on a depressed elderly
populationpopulation
UncontrolledUncontrolled testingtesting mortalitymortality
threats to validity:threats to validity: instrumentationinstrumentation restricted generalizability as control increasesrestricted generalizability as control increases
PRETESTPRETEST POST-TESTPOST-TEST
Post Test Only
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Post-TestOnlyControl Group Design
MeasurementMeasurement
of independentof independent
variablesvariables
MeasurementMeasurement
of dependentof dependent
variable(s)variable(s)
Randomly selectedRandomly selected
experimentalexperimentalgroupgroup
TREATMENTTREATMENT POST-TESTPOST-TEST
Randomly selectedRandomly selected
control groupcontrol group
Treatment:Treatment: Under control of researcherUnder control of researcher
Findings:Findings: comparison of experimental and control groupscomparison of experimental and control groups
Example:Example: Clochesy, Difani & Howe (1991). Electrode site preparation techniques: aClochesy, Difani & Howe (1991). Electrode site preparation techniques: a
follow-up studyfollow-up study
UncontrolledUncontrolled instrumentationinstrumentation
threats tothreats to mortalitymortality
validity:validity: limited generalizability as control increaseslimited generalizability as control increases
POST-TESTPOST-TEST
Ad t f Q i
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Advantages of Quasi-Experimental Designs
More Practical: EaseMore Practical: Ease
of implementationof implementation
More Feasible: resources,More Feasible: resources,
subjects, time, settingsubjects, time, setting
More Generalizable:More Generalizable:
Comparable to practiceComparable to practice
Advantages of
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Advantages ofExperimental Designs
More Controls: designMore Controls: design
& conduct of study& conduct of study
Increased internally valid:Increased internally valid:
decreased threats todecreased threats to
design validitydesign validity Fewer Rival HypothesesFewer Rival Hypotheses
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Outcomes Research
Agencies Supporting OutcomesAgencies Supporting Outcomes
ResearchResearch
Agency for Health ServicesAgency for Health Services
Research (AHSR)Research (AHSR)
Agency for Health Care PolicyAgency for Health Care Policy& Research (AHCPR)& Research (AHCPR)
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Outcomes Research
Structure of CareStructure of Care
System CharacteristicsSystem Characteristics
Provider CharacteristicsProvider Characteristics
Patient CharacteristicsPatient Characteristics
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Outcomes Research
Process of CareProcess of Care
Ordering testsOrdering tests
Treatments: pharmacologicalTreatments: pharmacological
& nonpharmacological& nonpharmacological
ReferralReferral
HospitalizationHospitalization
Counseling & educationCounseling & education
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Outcomes Research
OutcomesOutcomes
Clinical end pointsClinical end points Functional statusFunctional status
General well-beingGeneral well-being Satisfaction with careSatisfaction with care
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Critiquing A Design
Identify elements that wereIdentify elements that were
controlled in the studycontrolled in the study
Identify possible sources of biasIdentify possible sources of bias
Are there elements that couldAre there elements that could
have been controlled to improvehave been controlled to improve
the study design?the study design?
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Critiquing A Design
What elements of the design wereWhat elements of the design were
manipulated and how were theymanipulated and how were they
manipulated?manipulated? How adequate was the manipulation?How adequate was the manipulation?
What elements should have beenWhat elements should have been
manipulated to improve the validity ofmanipulated to improve the validity of
the findings?the findings?
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Critiquing A Design
Based on your assessment ofBased on your assessment of
the adequacy of the design,the adequacy of the design,how valid are the findings?how valid are the findings?
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Critiquing A Design
Is there another reasonableIs there another reasonable
(valid) explanation (rival(valid) explanation (rivalhypothesis) for the studyhypothesis) for the study
findings other than thatfindings other than that
proposed by the researcher?proposed by the researcher?
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Questions