Confounding Variable
A confounding variable is an extraneous variable that is correlated with the treatment variable and affects the response, but is not the treatment of interest. If a confounder is not equally distributed across treatment groups, it becomes a source of bias that prevents clear determination of the treatment effect.
Real World
A study found that ice cream sales and drowning deaths both rise in summer, but the confounding variable is temperature — warm weather independently drives both, so ice cream does not cause drowning.
Exam Focus
Explain how the confounder is linked to both the explanatory and response variables — identifying only one link loses a mark.
How well did you know this?