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Variables in research
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Every experiment tests whether changing one thing affects another. To design or evaluate research, you need to identify the variables.
Independent and dependent variables
Dependent variable (DV): the variable that is measured, to see if it has been affected by the IV.
Example: testing whether music affects memory. IV: whether music is playing or not. DV: the number of words recalled.
Variables should be operationalised: defined in a way that can be measured, for example 'number of words recalled out of 20' rather than 'memory'.
Extraneous variables
Situational variables: features of the environment or procedure, such as noise, temperature, time of day or the instructions given.
Participant variables: differences between the people taking part, such as age, intelligence, mood, tiredness or experience.
An extraneous variable that actually does change the results is sometimes called a confounding variable.
Spotting variables
A psychologist tests whether students recall more words in the morning or afternoon. Identify the IV and the DV.
- The researcher changes the time of day: that is the IV.
- The number of words recalled is measured: that is the DV.
Answer: IV: time of day (morning or afternoon). DV: number of words recalled.
The IV is changed by the researcher; the DV is measured. Extraneous variables can affect the DV: situational ones come from the environment, participant ones from differences between people. Variables should be operationalised so they can be measured.
The interactive lesson includes the diagrams for this topic.
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