This document outlines the key characteristics and components of an experimental research study. It discusses how experiments have an independent variable that is manipulated by the researcher to assess its effects on a dependent variable. Experiments use control and experimental groups, with participants randomly assigned, to test hypotheses about the impact of the independent variable while controlling for other unwanted variables. The example provided tests whether smoking marijuana affects driving performance by having participants either smoke marijuana or not before taking a driving simulator test.
2. Characteristics of an experiment
• IV is the variable selected and tested by the researcher to assess
effects on the DV (i.e participants responses)
• It is assumed that changes in the DV will result after exposure to the
IV.
• IV and potential unwanted variables (e.g extranious variables) are
controlled
• Use of random allocation of participants to different conditions
(groups) ensures uniform distributed participant characteristics
that can affect the DV.
3. Variables
Independent variable – the variable that is changed by the
experimenter, interested in its effect. We want to see the effect of
the IV on the DV
Dependent Variable – measures the effect of the
IV, see if the IV has effected the DV
5. Experimental group and Control group
Experimental group: Participants
exposed to the treatment condition, i.e
the IV manipulation.
Control group: Participants not
exposed to the IV manipulation.
6. The Research Hypothesis
Hypothesis – a testable prediction relating to the outcome of the
research being conducted, a prediction that one variable (IV) will
effect another variable (DV) in a certain way.
7. Example
Research Question: Does smoking marijuana effect driving
performance?
Independent Variable - smoking marijuana
Dependent Variable - driving performance
It is hypothesised that participants who smoke marijuana
will perform worse on a driving test as compared to
participants who have not smoked marijuana
8. The Operational Hypothesis
Variables that need to be operationalised
Smoking Marijuana
Driving Performance
The population – who we are testing
Operational Definitions
Smoking Marijuana – smoking one joint containing 500
milligrams of pure marijuana (not mixed with tobacco) 20
minutes before taking a driving test
Driving Performance -% score on VIC Roads, “Are you Road
Ready?”driving simulator
Population - Victorian drivers aged 18 – 25
9. The Operational Hypothesis
It is hypothesized that Victorian drivers aged 18 – 25 who
have smoked marijuana (smoking one joint containing
500 milligrams of pure marijuana 20 minutes before
taking a driving test) will perform worse on a driving test
(obtain a lower % score on the VIC Roads “Are you Road
Ready?” driving simulator) compared to participants who
have not smoked marijuana.
11. Extraneous and Confounding Variables
Extraneous Variable: Any variable, other than the IV, that can
cause a change in the DV and therefore affect the results of an
experiment in an unwanted way. An extraneous variable may
become a confounding variable.
Confounding variable: Any variable,
other than the IV, that is uncontrolled
and allowed to change together with
the IV, thereby having an unwanted
effect on the DV
