Think like a researcher: Experimental Design
An often overwhelming area for students - because memorisation won’t help you much here
Hypotheses
Hypothesis definition
When providing a hypothesis in an exam or SAC, your hypothesis must include:
- IV (Independent Variable)
- DV (Dependent Variable)
- The Study Population
- A Prediction (about the results of the experiment, comparing the results of the experimental group/s with the control group)
VCAA Psychology 2014 -‘A research hypothesis should state a prediction relating to the expected effect of an independent variable on a dependent variable as a means for testing a theory or for answering a specific research question. To score full marks, students need to:
- identify the research population
- identify the independent and dependent variables respectively
- state the predicted direction of the results if the hypothesis were true'
Dependant and Independant Varaible Definitions
Independent Variable: (The thing we are manipulating, or the thing we are studying)
The variable in an experiment which has been deliberately manipulated in order to measure its effect on the dependent variable.
Dependent Variable: (The result)
The dependent variable is the variable that is being measured in an experiment (such that we can see the effects of the independent variable on this variable).
Control and Experimental Groups
Control Groups: The group in the experiment that is not experiencing the Independent Variable (it is used a ‘baseline’ measurement to compare to the experimental group/s).
Experimental Group/s: The group/s that are experiencing the independent variable (there may be more than one group, with different ‘levels’ of experience to the independent variable)
Ideally, there should only be one difference between the control group, and the experimental group/s - the independent variable.
Extraneous and Confounding Variables
Extraneous Variable: Any variable that could alter the result of the dependent variable, that is not the independent variable (this includes controlled for variables).
(Potential) Confounding variables: Any variable other than the independent variable that has had (or we believe it has had, or that it most likely had) an ‘Potential’ is used because we haven’t controlled for this variable in the experimental design, and generally we are unware as to whether it is has or has not affected the results. We can only suggest/predict that it may have had an unwanted effect on the Dependent Variable.