QuasiExperimental Designs

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Quasi-Experimental Designs

• Quasi-experiment
• Conditions created by researcher or others
• Nonrandom assignment to conditions
• Usually intact groups
• McBurney any research or variable where the
  experimenter lacks complete control
• Evaluation research

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Nonequivalent control group designs

• Nonequivalent posttest only
• Selection, maturation confounds

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Nonequivalent control group pretest posttest
design

• Nonequivalent control group
• Control group is not randomly selected from the
  same population as the experimental group
• Nonequivalent groups assessed before and after
  intervention
• Interpreting results
• Clear

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Nonequivalent control group pretest posttest
design

• Interpreting results
• Not clear
• Regression

5
Nonequivalent control group pretest posttest
design

• Interpreting results
• Not clear
• Proportional

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Nonequivalent control group pretest posttest
design

• Interpreting results
• Clear

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Nonequivalent control group pretest posttest
design

• Attempt to eliminate all other explanations
• Identify variable producing any initial
  differences
• Focus on change in dependent variable

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Mixed factorial designs with non manipulated
variable

• Independent variables
• Customer race (manipulated within subject
  variable)
• Clerk race (subject variable)

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Designs without control groupstime series

• The one-group pretest-posttest design
• Lousy design
• Possible confounds
• Time series analysis
• Economics
• Rhythmical patterns
• Seasonal adjustments

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Interrupted Time Series Design

• Multiple measures before and after interruption
• Interruption independent variable

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Patterns
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Patterns
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Patterns
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Interrupted Time Series Design

• Threats to internal validity
• History
• Increase validity by use of multiple time series
• Non-equivalent control group time series

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Developmental and Evaluation Studies

• Developmental
• Cross-sectional
• Cohort effects
• Longitudinal
• Cross-sequential
• Different cohorts tested longitudinally
• Evaluation
• Formative
• Summative
• Four basic questions
• Program achieve goals
• What aspects contributed to success or failure
• Can the program be improved
• How valid is program theory
• Resistance to Program Evaluations