types of experiments

Question 1

lab experiment

Answer 1

In psychology, a laboratory is simply any situation that the researcher has complete control over.
One of the most common ways to gather evidence as it is high in scientific value and allows researchers to eliminate extraneous variables in order to establish cause and effect. You should be able to see the effect of the IV on the DV.

Strengths:
Good control of extraneous variables.
Easy to replicate
Easy to determine cause and effect.

Weaknesses:
Artificial situations may make participants behaviour unrepresentative - there might be a change in their behaviour.
Low ecological validity - can’t generalise findings.

Question 2

field experiment

Answer 2

In psychology, the term ‘field’ means the real world, therefore the experimenter does not have total control over the situation.
It involves the same process as a lab experiment (manipulating the IV and measuring the DV) but is applied to a more realistic setting than a laboratory.
In a field experiment, participants do not know they are taking part in a study, whereas in a lab experiment they do.

Strengths:
Behaviour is likely to be representative.
Lower demand characteristics than in lab as participants are unaware they are in a study.

Weaknesses:
Lower control over extraneous variables so researcher cannot be sure that any change in DV is due to IV.
Fewer controls so harder to replicate than lab.

Question 3

natural experiment

Answer 3

Conducted when it is not possible, for ethical or practical reasons to deliberately manipulate an IV. Therefore it is said that the IV varies ‘naturally’, tending to mean that there is a change in a group’s environment or situation and we measure a factor before and after the change.
Random allocation is not possible in natural experiments as there are fixed categories, e.g. fostered/adopted or biological family - we cannot change these.

Strengths:
Studying real life issues or problems as they occur - has high external validity.
Studies natural behaviours.

Weaknesses:
High chance of extraneous variables.
Unlikely to be able to replicate the experiment - low reliability.

Question 4

quasi experiment

Answer 4

Has an IV that varies between people.
Has not been made to occur by anyone, it is simply a difference between people that exists, e.g. looking at pre-existing differences between people such as gender, age etc.
Can be conducted in field or lab setting.

Strengths:
Controlled conditions means it can be replicated.

Weaknesses:
Cannot randomly allocate participants into a condition.
IV not deliberately changed by researcher, so we cannot claim the IV has caused the change in the DV.