RM: Types of experiment Flashcards
Laboratory experiment.
A controlled environment where extraneous and confounding variables (EVs and CVs) can be regulated.
Participants go to researcher.
The IV is manipulated and the effect of the DV is recorded.
Strengths of a laboratory experiment.
EVS AND CVS CAN BE CONTROLLED: this means that the effect of EVs and CVs on the DV can be minimised. Cause and effect on the IV and DV can be demonstrated (high internal validity)
CAN BE EASILY REPLICATED: due to the standardised procedure the experiment can be repeated. If the results are the same this confirms their validity.
Limitations of a laboratory experiment.
MAY LACK GENERALISABILITY: the controlled lab environment may be rather artificial and participants are aware they are being studied. Thus behaviour may not be ‘natural’ and can’t be generalised to everyday life (low external validity).
DEMAND CHARACTERISTICS: there 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.
Strengths of field experiments.
MORE NATURAL ENVIRONMENT: participants more comfortable in their own environment. Results may be more generalisable to everyday.
PARTICIPANTS UNAWARE OF BEING STUDIED: they are more likely to behave as they normally do so the findings can be generalised. The study has greater external validity.
Limitations of field experiments.
MORE DIFFICULT TO CONTROL CVS: observed changes in the DV may not be due to the IV, but to the CVs instead. It is more difficult to establish cause and effect than in the lab.
ETHICAL ISSUES: participants in a field experiment may not have given informed consent. This is an invasion of participants’ privacy, which raises ethical issues.
Natural experiments.
Experimenter doesn’t manipulate the IV. The IV would have varied even if the experimenter wasn’t interested.
DV may be naturally occurring (e.g. exam results) or may be measured by the experimenter.
Strengths of natural experiments.
MAY BE ONLY ETHICAL OPTION: it may be unethical to manipulate the IV, e.g. studying the effects of institutionalisation on children. A natural experiment may be the only way casual 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 expriences.
Limitations of natural experiments.
NATURAL EVENT MAY ONLY OCCUR RARELY: many natural events are ‘one-offs’ and this reduces the opportunity for research. This may limit the scope for generalising findings to other similar situations.
PARTICIPANTS NOT RANDOMLY SELECTED: experimenter has no control over which participants are placed in which condition as the IV is pre-existing. May result in CVs that aren’t controlled, e.g. Romanian orphans adopted early may also be the friendlier ones.
Quasi-experiments.
IV is based on a pre-existing difference between people, e.g. age or gender. No one has manipulated this variable, it simply exists.
DV may be naturally occurring (e.g. exam results) or may be measured by the experimenter.
Strengths of quasi-experiments.
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 casual conclusions.
COMPARISONS CAN BE MADE BETWEEN PEOPLE: in a quasi-experiment the IV is a difference between people, e.g. people with and without autism. This means that comparisons between different types of people can be made.
Limitations of quasi-experiments.
PARTICIPANTS NOT RANDOMLY ALLOCATED: experimenter has 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.
CASUAL RELATIONSHIPS NOT DEMONSTRATED: researcher does not manipulate/control the IV. We cannot say for certain that the change in the DV was due to the IV.
