Understanding Experiments: Design, Validity, and Applications, Slides of Sociology

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EXPERIMENTS

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Chapter Outline

 Topics Appropriate to Experiments  The Classical Experiment  Selecting Subjects  Variations on Experimental Design  An Illustration of Experimentation  Web-Based Experiments  “Natural” Experiments  Strengths and Weaknesses of the Experimental Method  Ethics and Experiments  Quick Quiz

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Topics Appropriate to

Experiments

 Well-suited for projects involving limited and well-defined concepts and propositions.  Hypothesis testing  Better suited for explanatory than descriptive  Small group interaction

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The Classical Experiment

 Major Components

1. Independent and Dependent Variables
2. Pre-testing and Post-testing
3. Experimental and Control Groups

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 Pre-testing – The measurement of a dependent variable along subjects.

 Post-testing – The measurement of a dependent variable among subjects after they have been exposed to an independent variable.

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 Experimental Group – A group of subjects to whom an experimental stimulus is administered.

 Control Group – A group of subjects to whom no experimental stimulus is administered and who should resemble the experimental group in all other respects.

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 Hawthorne Effect

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 The Double-Blind Experiment – An experimental design in which neither the subjects nor the experimenters know which is the experimental and which is the control group.

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 Probability Sampling

 Randomization – A technique for assigning experimental subjects to experimental and control groups.

 Matching – The procedure whereby pairs of subjects are matched on the basis of their similarities on one or more variables, and one member of the pair is assigned to the experimental group and the other to the control group.

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Figure 8.

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Figure 8.

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 Validity Issues in Experimental Research  Internal Validity – The possibility that the conclusions drawn from experimental results may not accurately reflect what went on in the experiment itself.  Sources: history (during exp, events happen outside that may confound the results),  maturation (subjects change over time),  testing (administering the test changes them),  instrumentation (changes in the survey for instance),  statistical regression (extreme scores necessarily level out over time even w/out IV),  selection bias (comparisons have no meaning unless the groups are comparable at the beginning of exp),  experimental mortality (some participants drop out),  demoralization (deprivation in the control group may lead to dropping out)

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Figure 8.4 – The Classical

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Figure 8.

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