Experimental method

to do for p2: design a study,

Types of experiments

Laboratory, Field, Natural, Quasi

Laboratory experiment

Controlled conditions, in which the researcher manipulates the IV and measures its effect on the DV. Controlled conditions to minimise the effect of EVs, to prevent them from becoming CVs that may affect the DV. Participants are aware due to the artificial nature of the situation.

Strength of laboratory experiments

High control of EVs as it uses standardised procedures. This should prevent CVs that affect the DV. This provides high internal validity to allow conclusions about cause and effect to be drawn between the IV and DV. High replicability

Limitations of laboratory experiments

Lacks external validity. The artificial nature means it lacks ecological validity

Findings cannot always be generalised beyond the lab (lacks mundane realism)

May have demand characteristics because participants are aware

Field experiment

natural conditions in which the researcher manipulates the IV and measures its effect on the DV. The ‘field’ is anywhere that is not a laboratory. Participants are unaware as they are observing natural behaviours.

Strengths of field experiments

Natural settings means it has high ecological validity so results are more representative of everyday life

High mundane realism

Limitations of field experiments

Low replicability

Low control over EVs due to natural setting so can become CVs and change findings

Ethical issues including not being able to give informed consent as they are unaware. So, the research may have a breach in privacy and a cost-benefit analysis will need to be conducted to ensure research outcomes will outweigh personal costs to those involved

Natural experiment

natural conditions, researcher does not manipulate the IV and instead examines the effect of an existing IV on the DV. The IV is naturally occurring (e.g. flood or earthquake - before vs after) and the behaviour of people affected is either compared to their own behaviour beforehand or with a control group who have not encountered the IV. The IV is natural, not the context where the investigation is taking place, as they may be tested in a lab. DV may be natural or not

Strengths of natural experiments

Unique insights gained into real life situations. High ecological validity

Natural IV means high external validity

Limitations of natural experiments

Low replicability

No control over EVs

Naturally occurring event may occur very rarely, so limits generalisability

Experiment

involves a change in IV and effect on the DV is measured or recorded

Quasi experiment

Controlled or natural conditions (mostly natural). Contains a naturally occurring IV (but one that already exists). IV is a difference between people (e.g. gender, age). Researcher examines the effect of IV on DV

Strengths of quasi experiments

Allows researchers to compare different types of people easily to provide insight that could not be ethically generated otherwise

When using lab conditions, it has high control and high replicability

Limitations of quasi experiments

Participants cannot be randomly allocated, so bias can occur

Has methodological issues e.g. when natural conditions are used, there is no control, so low replicability. When lab conditions are used, high control means it lacks ecological validity, as findings cannot be generalised

Role of experimental methods

find cause and effect relationships between IV and DV and measure the extent of the effect