Download presentation
Presentation is loading. Please wait.
1
9 Quantitative Research Designs
2
Learning Objectives Identify Criteria For Exploratory, Descriptive, And Explanatory Studies Define Experimental Research Differentiate Between Internal And External Validity In Experimental Designs Identify Six Threats To Internal Validity Identify Three Threats To External Validity
3
Learning Objectives Distinguish Among True Experimental, Quasi-Experimental, And Pre-Experimental Designs Describe Three True Experimental Designs Describe Two Quasi-experimental Designs Describe Two Pre-experimental Designs 3
4
Learning Objectives Discuss Four Types Of Nonexperimental Research Designs Recognize Two Types Of Settings In Which Research Is Conducted Identify Factors That Influence The Choice Of Research Designs Critique The Design Section Of Quantitative Studies 4
5
Learning Objective One Identify Criteria For Exploratory, Descriptive, And Explanatory Studies
6
Exploratory Studies Little known about phenomenon
Flexible data collection approach Qualitative and quantitative Hypotheses not appropriate
7
Descriptive Studies Phenomena described
Relationship between variables examined More information about variable(s) Test hypotheses
8
Explanatory Studies Explanations for relationships among phenomena
Rigorous Experimental research Control over research conditions Manipulate one or more variables
9
Learning Objective Two Define Experimental Research
9
10
Experimental Research
Cause + effect Manipulate and control independent variable Measure dependent variable
11
Problems With Experimental Research
Casual relationships difficult to establish Avoid using word prove Controls difficult to apply to human beings
12
Learning Objective Three Differentiate Between Internal And External Validity In Experimental Designs 12
13
Internal Validity Degree to which changes in effect can be attributed to cause Threats Other factors that influence dependent variable Constitute rival explanations or competing hypotheses
14
External Validity Degree to which results can be generalized
Questions to ask With 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 decreases As concern for external increases, internal may be affected Need to find balance
16
Learning Objective Four Identify Six Threats To Internal Validity
16
17
Six Threats to Internal Validity
Selection bias History Maturation Testing Instrumentation change Mortality
18
Selection Bias Results due to subject differences
Not due to independent variable manipulation Means to control Random group assignment
19
History Event other than the experimental treatment occurs during the course of study. Event influences dependent variable. Means to control Simultaneous control and comparison groups Random assignment of subjects to groups
20
Maturation Changes occur within subjects during study.
Changes influence the study results. Means to control Simultaneous control and comparison groups
21
Testing Influence of pretest or baseline data knowledge on posttest score
22
Instrumentation Change
Difference between pretest and posttest measurement Caused by change in accuracy rather than experimental treatment Means to control Judge training sessions Trial instrument runs to check for changes Continue to check instrument accuracy
23
Mortality Subject does not complete study.
Attrition rate different between groups Means to control No research design to control Establish strong researcher-participant relationship
24
Learning Objective Five Identify Three Threats To External Validity
24
25
Major Threats to External Validity
Hawthorne effect Experimenter effect Reactive effects of the pretest
26
Hawthorne Effect Participants’ responses influenced by knowing they are being observed Means to control Double-blind experiment
27
Experimenter Effect Experimental research
Researcher characteristics or behaviors influence subject behaviors. Examples of influential characteristics Facial expression Clothing Age Gender Body 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 pretest Examples of pretests Paper-and-pencil test Knowledge of baseline data
30
Difference Between Internal and External Pretest Threats
Internal threat: pretest or baseline data knowledge cause of posttest results External threat: pretest or baseline data knowledge catalyst (indirect cause)
31
Learning Objective Six Distinguish Among True Experimental, Quasi-Experimental, And Pre-Experimental Designs 31
32
Experimental Research Designs
True experimental Quasi-experimental Pre-experimental
33
True Experimental Design
Great deal of control Internal validity threats minimized Causality inferred with confidence
34
True Experimental Design Criteria
Researcher manipulates the experimental variable(s). One experimental group and one comparison group Subjects randomly assigned to groups
35
Quasi-Experimental Design
No comparison group Subjects not randomly assigned to groups
36
Advantages and Disadvantages of Quasi-Experimental Design
Real world more closely approximated Disadvantages Not as much control as true experimental design
37
Pre-Experimental Design
Considered weak Researcher has little control.
38
Learning Objective Seven Describe Three True Experimental Designs
38
39
Experimental Designs Pretest-posttest control group design
Posttest-only design Solomon four-group design
40
The Pretest-Posttest Control Group Design
Most frequently used experimental design Criteria Subjects randomly assigned to groups Pretest given to both groups Experimental 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)
Advantages Controls for all internal validity threats Controls for initial differences by adjusting posttest scores statistically Disadvantages External threat of reactive effects of the pretest Can only be generalized to situations in which pretest is administered
42
The Posttest-Only Control Group Design
Subjects randomly assigned to groups Experimental 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 out Eliminates 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— pretested Two 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 groups Advantages Minimizes threats to both internal and external validity Differences between groups can be associated with the experimental treatment. Disadvantages Requires a large sample Statistical analysis is complicated.
46
Learning Objective Eight Describe Two Quasi-Experimental Designs
46
47
Quasi-Experimental Designs
Nonequivalent control group design Time-series design
48
The Nonequivalent Control Group Design
Similar to pretest-posttest control group design No random assignment of subjects to groups
49
Internal Validity in Nonequivalent Control Group Design
Threats to internal validity controlled History Testing Maturation Instrumentation change Threats to internal validity that remain Selection 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 variable Strengthens validity Disadvantages Internal validity threats: history and testing
52
Learning Objective Nine Describe Two Pre-Experimental Designs
52
53
Pre-Experimental Designs
One-shot case study One-group pretest-posttest design
54
The One-Shot Case Study
Single group exposed to experimental treatment Observed after treatment Weak design Doesn’t control for threats to internal validity
55
The One-Group Pretest-Posttest Design
Comparison between a group of subjects before and after experimental treatment Threats to internal validity History Maturation Testing Instrumentation change
56
Learning Objective Ten Discuss Four Types Of Nonexperimental Research Designs
56
57
Nonexperimental Research
Describes phenomena as it exists No manipulation No control of variables
58
Nonexperimental Research (cont’d)
Survey research Correlational research Comparative research Methodological research
59
Survey Research Self-report data Phone Mail Internet Personal contacts
60
Strengths of Survey Research
Advantages Provide accurate information on populations Use relatively small samples Collect large amounts of data quickly Minimal cost Disadvantages Responses may be unreliable.
61
Correlational Research
Examines strength of relationship between two or more variables How is change in one variable associated with changes in another?
62
Correlational Coefficient
Indicates the strength and direction of relationships Indicates positive (+) or negative (–) information +1.00: perfect positive correlation –1.00: perfect negative correlation 0.00: no correlation or relationship
63
Comparative Studies Examines differences between groups on dependent variable No manipulation of the independent variable
64
Two Types of Comparative Studies
Retrospective or ex post facto Examine an effect Look back in time to determine cause Prospective Determination of a cause Looks forward in time to determine effect on subjects
65
Prospective Studies Advantages Prospective Experimental approach
Manipulate independent variable Prospective Costly
66
Methodological Studies
Research instruments and methods Development Testing Evaluation Seen with increasing frequency Develop stockpile of nursing-appropriate instruments
67
Secondary Analysis Studies
Analyses data gathered in previous study Test new hypotheses Ask new research questions Cost effective Efficient
68
Learning Objective Eleven Recognize Two Types Of Settings In Which Research Is Conducted
68
69
Research Settings Laboratory studies Field studies
70
Laboratory Studies Conducted in specially created environments
Research environment controlled by researcher
71
Field Studies Real-life setting
Little control maintained by researcher Very appropriate for nursing research
72
Learning Objective Twelve Identify Factors That Influence The Choice Of Research Designs
72
73
Cause and Effect Versus Describing a Phenomenon
Cause-and-effect research designs Experimental designs Describing a phenomenon research designs Nonexperimental designs
74
Level of Control Least control More control Most control
Pre-experimental designs More control Quasi-experimental designs Most control True experimental designs
75
Other Determinant Factors
Cost effective Secondary analysis studies Survey research Costly Prospective studies Ethical reasons Nonexperimental comparative studies
76
Learning Objective Thirteen Critique The Design Section Of Quantitative Studies
76
77
Critique of Quantitative Research Designs
Read the entire research report carefully Determine 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?
Similar presentations
