copyright c 2001 the mcgraw-hill companies, inc.1 chapter 8 quantitative research designs
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Copyright c 2001 The McGraw-Hill Companies, Inc. 1
Chapter 8
Quantitative Research Designs
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The Experimental Framework
Used to determine causation
Conducted in lab or other controlled setting To control for extraneous influences Independent variable is manipulated by
researcher
Participants randomly assigned to conditions or treatments
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The Classical Experiment
Researcher controls Selection of treatment & control groups – based
on theory Random assignment of participants to
conditions – ensures participants in each condition are equivalent before any treatment
Manipulation checks
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Posttest Experimental Design
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Pretest-Posttest Experimental Design
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Factorial Experimental Design
Treatment groups based on two or more independent variables
Dependent variable measured once after treatment given
Can test for main and interaction effects
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Longitudinal Experimental Designs
Multiple measurements of the dependent variable
Time between measurements depends on the nature of the communication phenomenon studied
Used for studying training effects or degree of retention
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Evaluating Experimental Design
Strengths
Researcher controls manipulation of IV
Assumes that any effect on DV is the cause of the IV
Precision
Limitations
Not all communication can be studied using experiments
Other external influence may be the cause of DV change
May not reflect reality
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Quasi-Experiments
Researcher relies on natural variation of independent variable
Posttest, pretest-posttest, factorial, and longitudinal designs can be used
Includes mock experiments, simulations, and field experiments
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Non-experimental Designs
Also called correlational or descriptive studiesResearcher does not control manipulation of IVParticipants not randomly assigned to conditionsPredictor and criterion are better labels for IV and DV as they do not imply causality
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Researcher Effects and Procedural Bias
Introduced in interaction with participants Similarity of researcher to participants How researcher communicates to participants Researcher unknowingly encourages desired
responses Demand characteristics created when topic has
socially desirable elements
Use research protocol to detail procedural steps
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Comparing Research Designs