Confounding and Extraneous Variables

WJEC PY3 revision on confounding and extraneous variables

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  • Created by: Flo
  • Created on: 04-06-12 12:10


Extraneous Variables

- Any other variable, other than the IV, that may affect the DV. These are anticipated and controlled by the experimenter to try to stop them becoming a confounding variable.

Confounding Variables

- Any variable, other than the IV, that has affected the DV. It was not controlled effectively so has affected the results

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How Confounding Variables might effect the Experim

Example; The Framing Effect

Social desirability bias - Students may have noticed the answer of their friends and chosen the same answer.

Individual differences - Some may be able to spot the deliberate simularity in the sotuations.

Experimenter Bias - Groups allocated non-randomly, task not explained clearly/differently.

Demand characteristics - Participants might be able to guess that there was a comparoson and different question on each sheet.

Situational factors - Time, temperature etc. may affect the results.

It is important that confounding varibles are minamalised in research as they reduce the validity (the extent to which changes in the DV can be attributed to changes in the IV)

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Solutions to Confounding Variables

Social Desirability Bias;

  • Answers filled out privetly / Reasurance of privacy

Individual differences;

  • Repeated measures design / Randomisation

Experimenter Bias;

  • Standardised Instructions / Double blind design

Demand characteristics;

  • Single blind design

Situational factors;

  • Controlled conditions
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