Type of experiment

• lab experiment:

  - controlled environment where EVs and CVs can be regulated

  - participants go to researcher

  - IV is manipulated and effect on DV is recorded
• lab experiment advantages:

  - EVs and CVs can be controlled: effect of EVs and CVs on DV can be minimised = high internal validity

  - can be more easily replicated: less chance new EVs are introduced = findings can be confirmed ... supporting their validity
• lab experiment disadvantages:

  - lack generalisability: artificial and participants may be aware they are being studied = behaviour may not be 'natural' = cannot be generalised to everyday life (low external validity)

  - demand characteristics: cues in the experimental situation that invite a particular response from participants = findings may be explained by these cues rather than the effect of the IV (lower internal validity)
• field experiment:

  - natural setting

  - experimenter goes to participant

  - IV is manipulated and effect on DV is recorded
• field experiment advantages:

  - more natural environment: participants are more comfortable and behaviour more authentic = more generalisable to everyday life

  - participants are unaware they are being studied: they are more likely to behave as they normally so findings can be generalised ... greater external validity / reduced demand characteristics
• field experiment disadvantages:

  - more difficult to control EVs/CVs: observed changes in the in the DV may not be due to the IV but EVs/CVs instead = more difficult to establish cause and effect than in the lab

  - ethical issues: participants in a field experiment may not have given informed consent = invasion of participants' privacy, which raises ethical issues
• natural experiment: - not manipulate the IV ... it does change but change is not made by the experimenter
• natural experiment advantages:

  - may be only practical / ethical option: may be unethical to manipulate the IV ... natural experiment may be only way casual research can be done on such topics (e.g. studying the effects of institutionalisation on children)

  - greater external validity: natural experiments involve real-world issues, such as the effect of a natural disaster on stress levels = findings more relevant to real experiences
• natural experiment disadvantages:

  - natural event may only occur rarely: many natural events are 'one-offs' so reduce opportunity for research = limit scope for generalising findings to other similar situations

  - participants are not randomly allocated: experimenter has no control over which participants are placed in which condition as the IV is pre-existing = CVs aren't controlled
• quasi-experiment: - IV is based on pre-existing difference between people (e.g. gender / age)
• quasi-experiment advantages:

  - controlled conditions: replication is possible

  - comparisons can be made between people
• quasi-experiment disadvantages:

  - participants are not randomly allocated: no control over which participants are placed in which condition as the IV is pre-existing ... participant variables may have caused the change in the DV acting as a CV