Experimental method: Natural and
quasi experiments
LO: To describe and evaluate different types of experiments in
psychological research.
Do Now: Identify whether these statements describe lab or field experiments.
1. High ecological validity because it is usually conducted in natural environmen
2. High level of control and it can be repeated.
3. No demand characteristics – usually the participants do not know they are be
studied – natural behaviour.
4. Scientific equipment can be used easily – no need of hiding from participants
5. Low ecological validity – the setting is not realistic.
6. Carried out in the real world.
SPEC CHECK: Experimental method. Types of experiment, laboratory and field experiments;
natural and quasi-experiments.
,Natural experiments
A natural experiment is not only conducted in the participants’ natural environ
but the independent variable is also naturally occurring and therefore outside
researcher’s control. The researcher is unable to control extraneous variables o
randomly allocate participants and merely measures the change in the depend
variable.
A well-known natural experiment in Helena,
Montana - smoking was banned from all public
places for a six-month period. Investigators
later reported a 60-percent drop in heart
attacks for the study area during the time the
ban was in effect.
, It is conducted when it is not possible to directly manipulate the IV
for ethical or practical reasons.
quasi experiments
LO: To describe and evaluate different types of experiments in
psychological research.
Do Now: Identify whether these statements describe lab or field experiments.
1. High ecological validity because it is usually conducted in natural environmen
2. High level of control and it can be repeated.
3. No demand characteristics – usually the participants do not know they are be
studied – natural behaviour.
4. Scientific equipment can be used easily – no need of hiding from participants
5. Low ecological validity – the setting is not realistic.
6. Carried out in the real world.
SPEC CHECK: Experimental method. Types of experiment, laboratory and field experiments;
natural and quasi-experiments.
,Natural experiments
A natural experiment is not only conducted in the participants’ natural environ
but the independent variable is also naturally occurring and therefore outside
researcher’s control. The researcher is unable to control extraneous variables o
randomly allocate participants and merely measures the change in the depend
variable.
A well-known natural experiment in Helena,
Montana - smoking was banned from all public
places for a six-month period. Investigators
later reported a 60-percent drop in heart
attacks for the study area during the time the
ban was in effect.
, It is conducted when it is not possible to directly manipulate the IV
for ethical or practical reasons.
