Types of experiment.

Laboratory experiment

An experiment that takes place in a controlled environment within which the researcher manipulates the IV and records the effect on the DV, whilst maintaining strict control of extraneous variables

Field experiment

An experiment that takes place in a natural setting within which the researcher maanipulates the IV and records the effect on the Dv

Natural experiment

An experiment where the change in IV is not brought about by the researcher but would have happened even if the researcher had not been there. The researcher records the effect on a DV they have decided.

Quasi experiment

A study that is almost an experiment but lacks key ingredients. The IV has not been determined by anyone (the researcher or any other person) - the variables simply exist, such as being old or young. Strictly speaking, this is not an experiment.

Benefits of lab experiment

High control of variables, reduced confounds and increases internal validity

Replication is easy, procedures are standardised so findings can be checked for reliability

Clear cause and effect relationships can be established

Negatives of lab experiments

Low ecological validity, artificial setting may not reflect real life

Demand characateristics , participants may behave unnaturally if they guess the aim.

Often low mundane realism, tasks may not resemble everyday behaviour

Field experiment strengths

High ecological validity, real world settings and behaviour.

More natural behaviour , participants less likely to change behaviour (reduced demand characteristics)

Can still test cause and effect (IV still manipulated)

Field experiments weaknesses

Less control over extraneous variables . reduces internal validity,

Difficuly to replicate due to real world conditions

Ethical issues (lack of informed consent or privacy concerns)

Natural experiment strengths

Can study rare or unethical situations that cannot be manipulated

High external validity because real world events are used

Useful for real life psychological issues (stress and trauma)

Natural experiment weaknesses

No control over IV or CVs, many confounding variables

Cannot establish clear cause and effect ( no direct manipulation)

May suffer from participant variables and lack of standardisation

Quasi experiment Strengths

Can study naturally occuring differences (e.g gender age and mental health)

Often more ethical than manipulating variables

Useful when true experiments are impossible

Quasi experiments weaknesses

No random allocation - participant variables may confound results

Cannot establish strong cause and effect

Often lower control over extraneous variables.