Types of Experiment Flashcards
Laboratory Experiment
A controlled environment where extraneous and confounding variables (EV’s and CV’s) can be regulated.
Participants go the researcher.
The IV is manipulated and the effect on the DV is recorded
Two Strengths of a Laboratory Experiment
+ EV’s and CV’s can be controlled. This means that the effect of EV’s and CV’s on the DV can be minimised. Cause and effect between the IV and DV can be demonstrated (high internal validity).
+ Can be easily replicated. Due to standardised procedure the experiment can be repeated. If the results are the same this confirms their validity
Two Limitations of a Laboratory Experiment
- May lack generalisability. The controlled lab environment may be rather artificial and participants are aware they are being studied. Therefore, behaviour may not be natural and can’t be generalised to everyday life (ie external validity).
- Demand characteristics may be a problem. These are cues in the experimental situation that invite a particular response from participants. The results of the experiment may be explained by these cues rather than the effect of the IV
Field Experiment
A natural setting.
The researcher goes to participants.
The IV is manipulated and the effect on the DV is recorded
Two Strengths of a Field Experiment
+ More natural environment. Participants more comfortable in their own environment. Results may be more generalisable to everyday.
+ Participants are unaware of being studied. They are more likely to behave as they normally do so the findings can be generalised. Therefore, the study has greater external validity
Two Limitations of a Field Experiments
- More difficult to control CV’s. Observed changes in the DV may not be due to the IV, but to CV’s instead. It is more difficult to establish cause and effect than in the lab.
- There are ethical issues. Participants in a field experiment may not have given informed consent. This is an invasion of privacy, which raises ethical issues
Natural Experiment
The experimenter does not manipulate the IV. The IV would have varied even if the experimenter wasn’t interested.
DV may be naturally occurring or may be measured by the experimenter
Two Strengths of a Natural Experiment
+ May be the only ethical option. It may be unethical to manipulate the IV. A natural experiment may be the only way causal research can be done for such topics.
+ Greater external validity. Natural experiments involve real-life issues, such as the effect of a natural disaster on stress levels. This means the findings are more relevant to real experiences
Two Limitations of a Natural Experiment
- The natural event may only occur rarely. Many natural events are rare and this reduced the opportunity for research. This may limit the scope for generalising findings to other similar situations.
- Participants are not randomly allocated. The experimenter has no control over which participants are placed in which condition as the IV is pre-existing. May result in CV’s that aren’t controlled
Quasi-Experiment
IV is based on a pre-existing difference between people. No one has manipulated this variable, it simply exists.
DV may be naturally occurring or may be measured by the experimenter
Two Strengths of a Quasi-Experiment
+ There is often high control. Often carried out under controlled conditions and therefore shares some of the strengths of lab experiments. This means increased confidence about drawing causal conclusions.
+ Comparisons can be made between people. In a quasi-experiment the IV is a difference between people. This means that comparisons between different types of people can be made
Two Limitations of a Quasi-Experiment
- Participants are not randomly allocated. The experimenter has no control over which participants are placed in which conditions as the IV is pre-existing. Participant variables may have caused the change in the DV acting as a CV.
- Causal relationships not demonstrated. The researcher doesn’t manipulate/control the IV. We can’t say for certain that any change in the DV was due to the IV
