Section 2.4: Dependent variables
From Research Methods in Psychology
[edit] WHAT ARE YOU STUDYING?
IN AN EXPERIMENT, THE EXPERIMENTER MEASURES THE DEPENDENT VARABLE. IN THIS SECTION WE WILL LOOK BRIEFLY AT DEPENDENT VARIABLES, HOWEVER WE COVER MEASUREMENT IN MUCH MORE DETAIL IN CHAPTER 5.
[edit] Dependent Variables
The dependent variable (DV) in an experiment is the variable that the experimenter measures to see what the effect was of the independent variable. It is dependent because it depends on (we hope) the independent variable. As with IVs, there is a great deal of choice about how you go about the DV. We will consider the operationalisation and measurement of dependent variables in much more detail in Chapter 5, however in this section we will have a quick look at some of the decisions that need to be made. We will use the example of the measurement of driving ability. If we are interested in using driving ability as a DV in an experiment (in other words, find out what affects driving ability), we have a very large choice of things that we could measure. Here are some ways we could do it.
- Ask someone to drive around a car park, avoiding obstacles (but how much do we penalise them for hitting an obstacle?)
- Ask someone to negotiate obstacles in a car park in reverse.
- Ask someone to drive around a course as quickly as possible.
- Test someone’s simple reaction time. (Stimulus appears, press a button).
- Test someone’s choice reaction time (stimulus appears, if the stimulus is red, press the right button, if green, press the left button).
- Test ability to recognise road signs.
- Test ability to make perceptual judgements of speed of cars.
- Test ability to make judgements of stopping distances of cars.
- Ask questions on the Highway Code.
- Use a driving simulator machine, to test speed of reaction to objects in the road.
Each of these tests is different, and may lead to a different assessment of ability, but each of them is one possible measure of driving ability. There are many ways of measuring dependent variables, but (usually) they can be broadly broken down into three different types: verbal measures, behavioural measures and physiological measures, and we will discuss these in Chapter 5.
[edit] Crucial Summary
This section has briefly examined the different ways in which dependent variables can be operationalised. We said that there were many different ways of operationalising different dependent variables, just as there were many ways of operationalising independent variables. We look much more closely at measurement in Chapter 5.
