Extraneous Variable
Essentially, an extraneous variable is any factor that can affect an experiment's dependent
variables, which are the controlled conditions. Since unexpected variables can change an
experiment's interpretation and results, it's important to learn how to control them.
Types of Extraneous Variables
(i) Demand characteristics: environmental clues which tell the participant how to
behave, like features in the surrounding or researcher’s non-verbal behaviour.
(ii) Experimenter / Investigator Effects: where the researcher unintentionally affects the
outcome by giving clues to the participants about how they should behave.
(iii) Participant variables, like prior knowledge, health status or any other individual
characteristic that could affect the outcome.
(iv) Situational variables, like noise, lighting or temperature in the environment.
TECHNIQUES OF CONTROLLING EXTRANEOUS VARIABLES
The following are the five important ways to control the extraneous variables:
(1) Technique of elimination
(2) Constancy of conditions
(3) Balancing
(4) Counterbalancing
(5) Randomization
These methods can be discussed as follows:
Technique of Elimination
The simplest way to control the extraneous variable is to eliminate it completely from the experimental
situation. For example, if noise in any experiment is an extraneous variable, the simple way to control it
is to make the experimental situation soundproof. But this technique is too simple to control many
extraneous variables. For example, controlling extraneous variables like age, sex, intelligence through
the technique of elimination is very difficult.
