Research Methods RE: Variables

Variables
Something that can be changed

IV:
Something the experimenter manipulates and is assumed to have an effect on the DV

DV:
The variable that is affected by the changes in the IV

Operationalising
In order for a hypothesis to be precise you need to operationalise the variables.
This is the process of devising a way of measuring a variable.
When the variables have been defined clearly and objectively the hypothesis will then be able to be tested precisely.

e.g. To see the effect of happiness on success in exams you would need to operationalise happiness (score on a scale of happiness)
Success in exams- the score they have on A level exams

Extraneous Variables:
General term for any variables other than the IV that might effect the DV.
Where EV's are important enough to provide alternative explanations for the effects, they become confounding variables
Extraneous Variables MIGHT effect the DV
Confounding Variables DO effect the DV

There are many different types of EV that need to be taken into account:

Situational Variables
e.g. Temperature, instructions, lighting
These can be controlled with standardisation by making sure conditions in the rooms are the same

Participant Variables
e.g. IQ, age, gender, personality
These are controlled through the design of the experiment. Matched participant design

In addition, other variables need to be controlled:
Demand Characteristics
Investigator effects