1. psychlotron.org.uk Today’s session You will learn aboutContext The difference between extraneous and confounding variables Detecting and correcting flaws in experiments Studies of social and cognitive psychology and individual differences

2. psychlotron.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

3. psychlotron.org.uk The world is not ideal All 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

4. psychlotron.org.uk All possible variables Extraneous variables Those that may affect the DV in some way Confounding variables Those that affect the two conditions differently

5. psychlotron.org.uk 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)

6. psychlotron.org.uk 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.