Experiments

What is it?

An experiment carried out in a controlled environment with all variables carefully controlled. Participants know they are taking part in the experiment although they may not know the true aims of the study.

Advantages

High internal validity (extraneous variables are controlled) which means that we can be confident the changes in the DV is due to the IV.

Can be easily replicated, demonstrating external validity.

Disadvantages

Participants know they are being studied which can change their behaviour so it is less natural (low ecological validity)

Participants may feel uncomfortable in an unknown setting (low ecological validity)

Low mundane realism 

What is it?

A controlled experiment conducted outside a laboratory. The IV is still manipulated by the experimenter there a causal relationship can still be demonstrated.

Advantages

Higher external validity (greater mundane realism).

Participants are not usually aware they are participating so their behaviour is more natural.

Disadvantages 

Lower internal validity (more difficult to control extraneous and confounding variables)

Ethical issue - Participants don't know they are being studies so its dificult to debrief them.

More time consuming and thus more expensive.

What is it?

Investigating the relationship between the IV and the DV in situations where the IV cannot be directly manipulated for ethical or practical reasons. The IV varies 'naturally' and the investigator records the effects it has on the DV. The DV may be tested in a laboratory.

Advantages

Allows research where IV cannot be manipulated for ethical or practical reasons.

Enables psychologists to studie 'real' problems such as effects of a disaster on health (increased mundame realism and ecological validity)

Disadvantages 

Cannot demonstrate causal relationships because IV is not directly manipulated.

Random allocation not possible, therefore there may be confounding variables that can't be controlled (threat to internal validity)

Can only be used where conditions vary naturally

What is it?

To investigate relationships between an IV and DV in situations where the IV is a characteristic of a person (e.g age or gender or level of depression)

Advantages

Allows comparisons between types of people.

Disadvantages 

Cannot demonstrate causal relationships because IV is not directly manipulated.

Random allocation not possible, therefore there may be confounding variables that can't be controlled (threat to internal validity)