research design for quantitative studies. characteristics of well designed research clearly defined...
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Research Design for Quantitative Studies
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
Research Design
Overall plan
– answer research questions
– test research hypotheses
Dimensions of Research Design
InterventionComparisonsControls for extraneous variablesTiming of data collectionResearch settingCommunication with subjects
Types of Research Design
Experimental Research
Quasi Experimental Research
Nonexperimental Research
Experimental Research
ManipulationControlRandomization
Experimental Designs
Basic Solomon Four-Group Factorial Repeated Measures Clinical Trials
Basic Experimental Designs
Posttest-onlyPretest-Posttest R=Randomization M=Measurement
X=Treatment
R X M-2
R M-1 X M-2
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
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
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
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
Randomized Clinical Trials
Distinctive application of experimental design
Involves testing of clinical treatmentRandom assignment of subjectsFocused on outcomesLarge and heterogenous sample
Advantages of Experimental Research
Powerful method of testing cause-effect relationships
Disadvantages of Experimental Research
Many variables not amenable to experimental manipulation
Ethical considerations may prevent experimental manipulation
May be impracticalHawthorne (placebo) effect
Quasi-Experimental Research
Involves manipulation of independent variable
Lacks either or both– Randomization
– Control Group
Quasi-Experimental Designs
Non-equivalent control group design
Time series design
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
Time Series Designs
One Group Data collection over extended time
period Experimental treatment during course
of data collection
Advantages and Disadvantages of Quasi-Experimental Design
Practical and feasible
Cannot make cause-effect inferences
Nonexperimental Research
No manipulative control of independent variables
Non-Experimental Designs
Ex Post Facto/Correlational research– Retrospective studies
– Prospective studiesDescriptive research
Advantages and Disadvantages of Non-experimental Research
Cannot infer causal relationshipsEfficient means of collecting large
amounts of data about problemRealistic
Additional Types of Quantitative Research
SurveyEvaluationNeeds AssessmentOutcomes Meta-analysis
Techniques of Research Control
External factors– constancy of
conditions– protocols
Techniques or Research Control
Intrinsic factors– Randomization– Homogeneity– Blocking– Matching– Statistical control
Threats to Internal Validity
History Testing Instrumentation Selection Maturation Mortality
External Validity
Generalizability of results– Validity– Reliability
Threats to External Validity
Hawthorne effect Novelty effect Interaction of history and treatment
effect Experimenter effect Measurement effect
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
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