Types of Variable > Extraneous Variable
What are Extraneous Variables?
Extraneous variables are any variables that you are not intentionally studying in your experiment or test. When you run an experiment, you’re looking to see if one variable (the independent variable) has an effect on another variable (the dependent variable). In an ideal world you’d run the experiment, check the results, and voila! Unfortunately…like many things in life…it’s a little more complicated that than. Other variables, perhaps ones that never crossed your mind, might influence the outcome of an experiment. These undesirable variables are called extraneous variables.
A simple example: you want to know if online learning increases student understanding of statistics. One group uses an online knowledge base to study, the other group uses a traditional text. Extraneous variables could include prior knowledge of statistics; you would have to make sure that group A roughly matched group B with prior knowledge before starting the study. Other extraneous variables could include amount of support in the home, socio-economic income, or temperature of the testing room.
Types of Extraneous Variables
- Demand characteristics: environmental clues which tell the participant how to behave, like features in the surrounding or researcher’s non-verbal behavior.
- Experimenter / Investigator Effects: where the researcher unintentionally affects the outcome by giving clues to the participants about how they should behave.
- Participant variables, like prior knowledge, health status or any other individual characteristic that could affect the outcome.
- Situational variables, like noise, lighting or temperature in the environment.
