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CHAPTER 7
THE EXPERIMENTAL RESEARCH STRATEGY
Goal of Experimental Research
Establish a cause-and-effect relationship between
two variables
Can we infer causality from relationships?
CAUSATION
THE DIRECTIONALITY PROBLEM
THE THIRD VARIABLE PROBLEM
Reverse causality
Problem of third variables
Establishing causal relationships
It is not sufficient to demonstrate
a relationship
An experiment manipulates one
variable while a second variable is measured and other variables are controlled.
Potential confounds must be
controlled
Experimental Research Terminology
Independent Variable (IV):
Dependent Variable (DV):
Experimental Group:
Control Group:
The Experiment
To test a hypothesis (e.g.,
exposure to marijuana increases appetite), an experimenter defines the
variables of the hypothesis:
Cause: Independent variable (IV)
Effect: Dependent variable (DV)
The experimenter manipulates the IV
and measures the DV to test the hypothesis
Active Learning Exercise 1
Active Learning Exercise 2
For each of the following, identify
the IV, DV, Experimental Group(s), Control Group
The IV
The DV
The experimental group
The control group
Increasing External Validity
Simulation:
Field Studies: an experiment conducted in a
place that the participant perceives as a natural environment.
Strength of
Manipulation
A
strong manipulation maximizes the differences between the groups and increases
the chances that the IV will have an effect on the DV.
Straightforward
Manipulations
The
levels of the IV are changed directly for each condition of the experiment.
§
Variables are manipulated via presenting written, verbal, or visual
material to participants.
§
You can also manipulate variables via the type of instructions given to
the participants.
Staged
Manipulations
Sometimes it is necessary to stage events that occur during the experiment to
manipulate the IV successfully.
1.
2. They attempt to simulate realworld situations.
Staged
Manipulations
Staged manipulations often employ a confederate. The confederate appears to be
another participant in an experiment but is actually part of the manipulation.
Studies that utilized confederate(s)
Milgrams obedience studies
Aschs conformity study
Conformity
SANDSS Study
McGuire and colleagues
Observational measure of reactions to the
unfamiliar
With an
unfamiliar adult
Alone
With an
unfamiliar child
Exploratory behavior
Manipulation Check
A
manipulation check is a way to see whether you have manipulated what you thought
you manipulated.
Ways to do manipulation checks:
a.
b.
Interview subjects after study
Class Activity