Control of variables
Cards (11)
- The extraneous variable is any variable other than the independent variable that can affect the dependent variable if it is not controlled.
- The confounding variable is a type of extraneous variable that was not controlled. This means we canāt tell if any change in the dependent variable is due to the independent variable or the confounding data.
- Extraneous variables include:
- Situational variables
- Participant variables
- Experimenter bias
- Demand characteristics
- Order effects
- Participant variables are individual differences between participants e.g. age, intelligence, mood etc.
- Situational variables are factors in the environment that can affect participantsā behaviour e.g. noise, lighting, temperature etc.
- Experimenter variables (investigator effects) are behaviours or characteristics of the researcher that might influence participants e.g. body language, tone of voice etc.
- Demand characteristics are cues in the experimental situation that reveal the aim of the study to participants, potentially affecting their behaviour.
- Order effects occur in repeated measures designs and they arise from the order in which participants experience conditions e.g. fatigue, boredom or practice effects.
- Methods to control for extraneous variables:
- Randomisation
- Standardisation
- Counterbalancing
- Blinding
- Randomisation is the use of chance to reduce the researcherās influence on the design of the study e.g. randomly allocating the participants to conditions or randomising the order of tasks.
- Standardisation is ensuring all participants have the same procedures and instructions. This reduces the influence of situational variables.