Is this an experiment?

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Is this an experiment?

• A researcher wanted to investigate the effect of
  gender on driving ability when talking. She
  recruited a group of male and female university
  students and matched them for how long they had
  held a driving licence for and how far they drove
  each week. She measured the number of collisions
  they made operating a driving simulation whilst
  responding verbally to a verbal reasoning task.

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Todays session
You will learn about Context
Quasi experiments and group comparison studies Identifying distinguishing between experiments and non-experiments Internal-external validity tradeoffs in experimental design Studies of social and cognitive psychology and individual differences
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In a true experiment...

• In a true experiment...
• An IV is manipulated in a controlled manner
• Extraneous variables are controlled
• A DV is measured to see if it changes
• Quasi-experiments share features with true
  experiments, but do not meet all of these
  criteria

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The effect of stress on errors
True experiment
PPs randomly allocated to two conditions
Based on Coolican (2001)
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The effect of stress on errors
Quasi experiment
Based on Coolican (2001)
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The effect of stress on errors
Group difference study
Questionnaire used to identify...
Based on Coolican (2001)
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• Why would a researcher prefer to use a true
  experiment over a quasi experiment or group
  difference study?

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• Given their limitations, what justification is
  there for using quasi experiments and group
  difference studies?

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Validity tradeoffs

• Increased control over the research situation
  increases the internal validity
• Increased realism in the research situation
  increases the ecological validity

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High internal validity
Low ecological validity
High ecological validity
Low internal validity