1.
RESEARCH METHODS
- EXPERIMENTS

2.
EXPERIMENTS
Experiment: investigation which is looking for cause and
effect relationship.
IV: the factor under investigation in which an IV is
manipulated and is responsible for changes in the DV
DV: the factor which is measured and is expected to change
under the influence of the IV
Extraneous variable: variable that randomly affects the DV n
all levels of the IV or systematically.
Control condition: a level of the IC in an experiment from
which the IC is absent. It is compared to one or more
experimental conditions.

3.
EXPERIMENTAL DESIGNS
Independent measures design
Repeated measures design
Matched pair design

4.
Independent measures
design: design in which a
different group of
participants is used for
each level of the IV or
conditions
Repeated measures
design: design in
which each
participant persons in
every level of the IV.
Match pair design:
design in which
participants are
arranged into pairs.
• Demand
Characteristics
• Random Allocation
• Participant Variable
• Order Effect
• Practice Effect
• Fatigue Effect
• Counterbalancing
• Matched based on age,
gender, intelligence,
personality

5.
Demand characteristics: features of the experiment that give away the aim – may cause
participants to change their behaviour.
Random allocation: participants are put in to levels of the IV such that each person has an equal
chance of being in any condition – eliminates individual differences.
Participant variables: individual differences between participants that could affect their behaviour –
could hide or exaggerate difference between conditions.

6.
Order effect: consequences of participating in a study more than once – practice &
fatigue effects. Can cause changes in behaviour that are not due to the IV.
Practice effect: situation where participants’ performance improves because they
experience the experimental task more than once – familiarity
Fatigue effect: situation where participants’ performance declines because they
experience the task more than once – boredom, tiredness
Counterbalancing: used to overcome order effects. ABBA design – half the
participants do condition A then B, other half does condition B then A.

7.
EVALUATIONS
OF
EXPERIMENTAL
DESIGNS

8.
TYPES OF EXPERIMENTS
Laboratory Experiment
• Conducted in artificial setup
• Participants may not be in the usual environment
• Strict controls over the situation
Field Experiment
• Causal relationship in which an IV is manipulated and is expected to be responsible for changes in the DV.
• Conducted in the normal environment of the participant
Natural Experiment
• Look for a causal relationship in which the IV cannot be directly manipulated by the experimenter
• Studies the effect of an existing difference or change

9.
TERMS
Standardization: keeping the procedure for each participant exactly the
same – ensures changes are due to variables under investigation
Validity: the extent to which the researcher is testing what they claim to be
testing.
Reliability: the extent to which a procedure, task or measure is consistent
Generalize: apply the findings of a study more widely Eg: other
settings & other populations
Ecological validity: extent to which the findings of research in one
would generalize to other situations
Uncontrolled variable: a confounding variable that may not have been
identified & eliminated which can confuse results

10.
EVALUATIONS
OF EACH
EXPERIMENT

11.
ETHICS IN EXPERIMENTS
• Participants should know enough about a study to decide
whether they want to participate
Informed consent
• A participant should know they can remove themselves,
and their data from the study at any time.
Right to withdraw
• Participants’ emotions and physical space should not be
invaded
Privacy
• Participants’ results & personal information should be
kept safely and not released to anyone outside the study
Confidentiality