Psychlotron.org.uk Today’s session You will learn aboutContext The difference between extraneous...
Transcript of Psychlotron.org.uk Today’s session You will learn aboutContext The difference between extraneous...
psyc
hlot
ron.
org.
uk
Today’s session
You will learn about Context
The difference between extraneous and confounding variablesDetecting and correcting flaws in experiments
Studies of social and cognitive psychology and individual differences
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org.
uk
The experimental method
PPs complete task under two
conditions
IV set for condition A
IV set for Condition B
DV measurements for A & B
compared
In an ideal world, the only variation within the DV measurements would be that caused by the
manipulation of the IV
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The world is not idealAll the variability in the DV scores
Variability in DV caused by the IV Variability in DV caused by error
This is spread randomly across the
scores of both conditions
This affects the scores of one
condition differently from the
other
Random error
Systematic error
Systematic error
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All possible variables
Extraneous variables Those that may affect the DV in some way
Confounding variables Those that affect the two conditions differently
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• Non-confounding extraneous variables increase ‘noise’, making measurement unclear
• Confounding extraneous variables act as ‘extra IVs’ leading to mistaken conclusions about what has affected the DV (internal validity)
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Bickman (1975)
• List some extraneous variables that might have been present in this experiment. Identify at least one that might have produced a random error and one that might have confounded the results (i.e. produced a systematic error) if left uncontrolled.