Control of Extraneous Variables (Psychology Research Methods Explained)

When research is planned, it’s important to anticipate all the factors that might affect the behaviour under scrutiny but which are not the focus of the research. The term for these factors is extraneous variables.
We do not want extraneous variables to influence the Dependant Variable, because then we cannot distinguish the differences between the two conditional groups. Extraneous variables can be separated into three classes.