Experimental Design Booklet 2

Define a Lab experiment

Define a Lab experiment

An experiment conducted in a highly controlled environment

Define a Field experiment

An experiment where the IV is manipulated in a natural, more everyday setting (in the experiment’s field)

Define a Natural experiment

An experiment where the researcher takes advantage of a pre-existing independent variable

Define a Quasi experiment

An experiment based on an existing differences between people (gender)

Give strengths and limitations of lab experiments

Strengths:

• High internal validity (can be more certain about cause and effect)

• More easily replicable than other experiment types

Limitations:

• Low external validity (results may not apply to real life as experiment performed in artificial environment)

• Demand characteristics more likely

• Low mundane realism (tasks are not representative of real life situations)

Give strengths and limitations of field experiments

Strengths:

• High external validity (environment is more natural therefore behaviour of participants is more representative of ‘real life’ behaviour

Limitations:

• Lack of control of extraneous variables (may not be measuring the effect of the IV on the DV)

• Hard to replicate

• Ethical issues due to lack of consent

Give strengths and limitations of natural experiments

Strengths:

• High external validity (environment is more natural therefore behaviour of participants is more representative of ‘real life’ behaviour

• Researcher is taking advantage of a situation which will happen regardless of their study (could make experiment more ethical as participants are not forced into an artificial situation)

Limitations:

• Researcher does not manipulate the IV so experiment is very difficult to replicate

• Participants are not randomly assigned to experimental conditions so hard to see if IV has caused effect on the DV

Give strengths and limitations of Quasi experiments

Strengths:

• Often carried out in controlled conditions so shares the same strengths as lab

Limitations:

• Quasi experiments cannot randomly allocate people to experimental conditions therefore extraneous variables may affect the outcome