psychlotron.org.uk is this an experiment? a researcher wanted to investigate the effect of gender on...
TRANSCRIPT
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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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Today’s session
You will learn about Context
Quasi experiments and group comparison studiesIdentifying & distinguishing between experiments and non-experimentsInternal-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
High stress condition
Low stress condition
Number of errors measured
Based on Coolican (2001)
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The effect of stress on errors
Quasi experiment
High stress condition
Low stress condition
Number of errors measured
Based on Coolican (2001)
Night shift
Day shift
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The effect of stress on errors
Group difference study
Questionnaire used to
identify...
High stress PPs
Low stress PPs
Number of errors measured
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 internal validity
Low ecological validity High ecological validity