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Research Design for Quantitative Studies

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Presentation on theme: "Research Design for Quantitative Studies"— Presentation transcript:

1 Research Design for Quantitative Studies

2 Characteristics of Well Designed Research
Clearly defined research question Clearly defined population under study Clearly defined sampling procedure Clearly defined variables of interest Clearly defined statistical method Statement of the null hypothesis, Ho: Statement of the alternative hypothesis, Ha: Collection of sample under appropriate conditions Analysis and report

3 Research Design Overall plan answer research questions
test research hypotheses

4 Dimensions of Research Design
Intervention Comparisons Controls for extraneous variables Timing of data collection Research setting Communication with subjects

5 Types of Research Design
Experimental Research Quasi Experimental Research Nonexperimental Research

6 Experimental Research
Manipulation Control Randomization

7 Experimental Designs Basic Solomon Four-Group Factorial
Repeated Measures Clinical Trials

8 Basic Experimental Designs
Posttest-only Pretest-Posttest R=Randomization M=Measurement X=Treatment R X M-2 R M-1 X M-2

9 Solomon Four-Group Design
Data Collection Group Before After Experiment-pretest X X Experiment-no pretest X Control-pretest X X Control-no pretest X

10 Factorial Design Permits the testing of multiple hypotheses in a single experiment Permit evaluation of main effects as well as interaction effects Subjects randomly assigned to some combination of treatments Independent variables known as factors Each factor has two or more levels

11 Factorial Design Type of Stimulation Auditory(A1) Tactile (A2)
15 min (B1) A1 B1 A2 B1 30 Min (B2) A1 B2 A2 B2 45 Min (B3) A1 B3 A2 B3

12 Repeated Measures Design
Also known as crossover design Exposure of same subjects to more than one experimental treatment Participants must be randomly assigned to different orderings of treatment Ensures highest possible equivalence among subjects exposed to different conditions May have carry-over effects

13 Randomized Clinical Trials
Distinctive application of experimental design Involves testing of clinical treatment Random assignment of subjects Focused on outcomes Large and heterogenous sample

14 Advantages of Experimental Research
Powerful method of testing cause-effect relationships

15 Disadvantages of Experimental Research
Many variables not amenable to experimental manipulation Ethical considerations may prevent experimental manipulation May be impractical Hawthorne (placebo) effect

16 Quasi-Experimental Research
Involves manipulation of independent variable Lacks either or both Randomization Control Group

17 Quasi-Experimental Designs
Non-equivalent control group design Time series design

18 Nonequivalent Control Group Designs
Involves experimental treatment and two or more groups of subjects Comparison group rather than control group Quasi-experimental versus pre-experimental

19 Time Series Designs One Group
Data collection over extended time period Experimental treatment during course of data collection

20 Advantages and Disadvantages of Quasi-Experimental Design
Practical and feasible Cannot make cause-effect inferences

21 Nonexperimental Research
No manipulative control of independent variables

22 Non-Experimental Designs
Ex Post Facto/Correlational research Retrospective studies Prospective studies Descriptive research

23 Advantages and Disadvantages of Non-experimental Research
Cannot infer causal relationships Efficient means of collecting large amounts of data about problem Realistic

24 Additional Types of Quantitative Research
Survey Evaluation Needs Assessment Outcomes Meta-analysis

25 Techniques of Research Control
External factors constancy of conditions protocols

26 Techniques or Research Control
Intrinsic factors Randomization Homogeneity Blocking Matching Statistical control

27 Threats to Internal Validity
History Testing Instrumentation Selection Maturation Mortality

28 External Validity Generalizability of results Validity Reliability

29 Threats to External Validity
Hawthorne effect Novelty effect Interaction of history and treatment effect Experimenter effect Measurement effect

30 Nursing Studies Are---
Usually nonexperimental Most commonly use correlational design More often retrospective than prospective More likely to use analysis of covariance and similar techniques to control intrinsic factors Typically limited in terms of external validity

31 Tips for Enhancing Research Conrol
Strategies to control external factors Maximize constancy of conditions Strategies to control study participants Strong research design Measurement of demographic variables Identify extraneous variables via review of literature

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