2 Learning ObjectivesIdentify Criteria For Exploratory, Descriptive, And Explanatory StudiesDefine Experimental ResearchDifferentiate Between Internal And External Validity In Experimental DesignsIdentify Six Threats To Internal ValidityIdentify Three Threats To External Validity
3 Learning ObjectivesDistinguish Among True Experimental, Quasi-Experimental, And Pre-Experimental DesignsDescribe Three True Experimental DesignsDescribe Two Quasi-experimental DesignsDescribe Two Pre-experimental Designs3
4 Learning ObjectivesDiscuss Four Types Of Nonexperimental Research DesignsRecognize Two Types Of Settings In Which Research Is ConductedIdentify Factors That Influence The Choice Of Research DesignsCritique The Design Section Of Quantitative Studies4
5 Learning Objective One Identify Criteria For Exploratory, Descriptive, And Explanatory Studies
6 Exploratory Studies Little known about phenomenon Flexible data collection approachQualitative and quantitativeHypotheses not appropriate
7 Descriptive Studies Phenomena described Relationship between variables examinedMore information about variable(s)Test hypotheses
8 Explanatory Studies Explanations for relationships among phenomena RigorousExperimental researchControl over research conditionsManipulate one or more variables
9 Learning Objective Two Define Experimental Research 9
10 Experimental Research Cause + effectManipulate and control independent variableMeasure dependent variable
11 Problems With Experimental Research Casual relationships difficult to establishAvoid using word proveControls difficult to apply to human beings
12 Learning Objective Three Differentiate Between Internal And External Validity In Experimental Designs12
13 Internal ValidityDegree to which changes in effect can be attributed to causeThreatsOther factors that influence dependent variableConstitute rival explanations or competing hypotheses
14 External Validity Degree to which results can be generalized Questions to askWith what degree of confidence can findings be transferred to the entire population?Will these findings hold true with other groups and in other times and places?
15 Relationship Between Internal and External Validity As control for internal increases, external decreasesAs concern for external increases, internal may be affectedNeed to find balance
16 Learning Objective Four Identify Six Threats To Internal Validity 16
17 Six Threats to Internal Validity Selection biasHistoryMaturationTestingInstrumentation changeMortality
18 Selection Bias Results due to subject differences Not due to independent variable manipulationMeans to controlRandom group assignment
19 HistoryEvent other than the experimental treatment occurs during the course of study.Event influences dependent variable.Means to controlSimultaneous control and comparison groupsRandom assignment of subjects to groups
20 Maturation Changes occur within subjects during study. Changes influence the study results.Means to controlSimultaneous control and comparison groups
21 TestingInfluence of pretest or baseline data knowledge on posttest score
22 Instrumentation Change Difference between pretest and posttest measurementCaused by change in accuracy rather than experimental treatmentMeans to controlJudge training sessionsTrial instrument runs to check for changesContinue to check instrument accuracy
23 Mortality Subject does not complete study. Attrition rate different between groupsMeans to controlNo research design to controlEstablish strong researcher-participant relationship
24 Learning Objective Five Identify Three Threats To External Validity 24
25 Major Threats to External Validity Hawthorne effectExperimenter effectReactive effects of the pretest
26 Hawthorne EffectParticipants’ responses influenced by knowing they are being observedMeans to controlDouble-blind experiment
27 Experimenter Effect Experimental research Researcher characteristics or behaviors influence subject behaviors.Examples of influential characteristicsFacial expressionClothingAgeGenderBody build
28 Rosenthal Effect Nonexperimental research Interviewer characteristics or behaviors influence respondent’s answers.
29 Reactive Effects of the Pretest Subjects sensitized to experimental treatment because of pretestExamples of pretestsPaper-and-pencil testKnowledge of baseline data
30 Difference Between Internal and External Pretest Threats Internal threat: pretest or baseline data knowledge cause of posttest resultsExternal threat: pretest or baseline data knowledge catalyst (indirect cause)
31 Learning Objective Six Distinguish Among True Experimental, Quasi-Experimental, And Pre-Experimental Designs31
32 Experimental Research Designs True experimentalQuasi-experimentalPre-experimental
33 True Experimental Design Great deal of controlInternal validity threats minimizedCausality inferred with confidence
34 True Experimental Design Criteria Researcher manipulates the experimental variable(s).One experimental group and one comparison groupSubjects randomly assigned to groups
35 Quasi-Experimental Design No comparison groupSubjects not randomly assigned to groups
36 Advantages and Disadvantages of Quasi-Experimental Design Real world more closely approximatedDisadvantagesNot as much control as true experimental design
37 Pre-Experimental Design Considered weakResearcher has little control.
38 Learning Objective Seven Describe Three True Experimental Designs 38
39 Experimental Designs Pretest-posttest control group design Posttest-only designSolomon four-group design
40 The Pretest-Posttest Control Group Design Most frequently used experimental designCriteriaSubjects randomly assigned to groupsPretest given to both groupsExperimental group receives experimental treatment.Comparison group receives routine treatment or no treatment.Posttest given to both groups
41 The Pretest-Posttest Control Group Design (cont’d) AdvantagesControls for all internal validity threatsControls for initial differences by adjusting posttest scores statisticallyDisadvantagesExternal threat of reactive effects of the pretestCan only be generalized to situations in which pretest is administered
42 The Posttest-Only Control Group Design Subjects randomly assigned to groupsExperimental group receives the experimental treatment.Comparison group receives routine treatment or no treatment.Posttest given to both groups
43 Advantages of Posttest-Only Control Group Design Easier to carry outEliminates reactive effects of the pretest on the posttest
44 The Solomon Four-Group Design All subjects are randomly assigned to one of four groups.Two groups—experimental group 1 and comparison group 1— pretestedTwo groups—experimental group 1 and experimental group 2—receive experimental treatment.Two groups—comparison group 1 and comparison group 2—receive routine treatment or no treatment.
45 Solomon Four-Group Design Posttest given to all four groupsAdvantagesMinimizes threats to both internal and external validityDifferences between groups can be associated with the experimental treatment.DisadvantagesRequires a large sampleStatistical analysis is complicated.
46 Learning Objective Eight Describe Two Quasi-Experimental Designs 46
47 Quasi-Experimental Designs Nonequivalent control group designTime-series design
48 The Nonequivalent Control Group Design Similar to pretest-posttest control group designNo random assignment of subjects to groups
49 Internal Validity in Nonequivalent Control Group Design Threats to internal validity controlledHistoryTestingMaturationInstrumentation changeThreats to internal validity that remainSelection bias
50 Time-Series Design Periodic observations or measurements of subjects Experimental treatment administered between two of the observations
51 Time-Series Design Advantages Disadvantages Numerous observations or measurements of dependent variableStrengthens validityDisadvantagesInternal validity threats: history and testing
52 Learning Objective Nine Describe Two Pre-Experimental Designs 52
53 Pre-Experimental Designs One-shot case studyOne-group pretest-posttest design
54 The One-Shot Case Study Single group exposed to experimental treatmentObserved after treatmentWeak designDoesn’t control for threats to internal validity
55 The One-Group Pretest-Posttest Design Comparison between a group of subjects before and after experimental treatmentThreats to internal validityHistoryMaturationTestingInstrumentation change
56 Learning Objective Ten Discuss Four Types Of Nonexperimental Research Designs 56
57 Nonexperimental Research Describes phenomena as it existsNo manipulationNo control of variables
58 Nonexperimental Research (cont’d) Survey researchCorrelational researchComparative researchMethodological research
60 Strengths of Survey Research AdvantagesProvide accurate information on populationsUse relatively small samplesCollect large amounts of data quicklyMinimal costDisadvantagesResponses may be unreliable.
61 Correlational Research Examines strength of relationship between two or more variablesHow is change in one variable associated with changes in another?
62 Correlational Coefficient Indicates the strength and direction of relationshipsIndicates positive (+) or negative (–) information+1.00: perfect positive correlation–1.00: perfect negative correlation0.00: no correlation or relationship
63 Comparative StudiesExamines differences between groups on dependent variableNo manipulation of the independent variable
64 Two Types of Comparative Studies Retrospective or ex post factoExamine an effectLook back in time to determine causeProspectiveDetermination of a causeLooks forward in time to determine effect on subjects
76 Learning Objective Thirteen Critique The Design Section Of Quantitative Studies 76
77 Critique of Quantitative Research Designs Read the entire research report carefullyDetermine if the appropriate design is used
78 Questions for Critique of the Design Section of Quantitative Studies Is the design clearly identified and described?Is the design appropriate to test the hypothesis or hypotheses or research question(s)?If an experimental design was used, was it appropriate?
79 Questions for Critique of the Design Section of Quantitative Studies If an experimental design was used, what means were used to control for threats to internal and external validity?Was the assignment of subjects to experimental and control groups clearly described?Does the research design allow the researcher to draw a cause-and-effect relationship between the variables?
80 Questions for Critique of the Design Section of Quantitative Studies If a nonexperimental design was used, would an experimental design have been more appropriate?If a nonexperimental design was used, what means were used to control for extraneous variables?