Types Of Experiment Flashcards
Laboratory experiment
Conducted in a highly controlled environment. Not always a lab- could be a classroom where conditions are well controlled.
Strengths of laboratory experiments
High control over confounding and extraneous variables. Means researchers can ensure any effect on the DV is result of manipulation of IV. Thus cause and effect (high internal validity).
Replication is more possible than in other types of experiment because of the high level of control. This ensures new extraneous variables are not introduced when repeating an experiment. Replication is vital to see whether results are valid.
Limitation of Laboratory experiments
May lack generalisability. Lab environment may be artificial and not like everyday life. In unfamiliar context participants may behave in unusual ways so their behaviour cannot always be generalised beyond the research setting (low external validity)
Participants usually aware they are being tested, may give rise to unnatural behaviour-demand characteristics.
Tasks participants are asked to carry out in a lab experiment may not represent everyday experience, like recalling lists of words (low mundane realism)
Field experiments
IV is manipulated in a natural, more everyday setting (in the field). The researcher goes to the participants usual environment rather than lab experiments where participants go to lab.
Strengths of field experiments
Higher mundane realism than lab because environment in more natural. Produce behaviour which is more valid and authentic. Participant may not be aware they are being studied (high external validity)
Limitations of field experiments
Increased realism means loss of control of confounding variables and extraneous variables. Cause and effect between IV and DV variables may be more difficult to establish, precise replication is often not possible.
Ethical issues, participants may not be aware they are being studied, can’t consent to being studied, invasion of privacy.
Natural experiments
Like a lab or field insofar as the researcher measures the effect of an IV on a DV. However researcher has no control over IV and can’t change it-someone or something else causes IV to vary. Eg before and after a natural disaster.
The IV is natural, not necessarily the setting-participants may still be tested in lab. DV may also be natural.
Strengths of natural experiment
Provide opportunities for research that may not otherwise be undertaken for practical or ethical reasons, such as institutionalised Romanian orphans.
Natural experiments often have high external validity because they involve the study of real-world issues and problems as they happen. Eg effects of natural disaster on stress levels.
Limitations of natural experiments
Naturally occurring event may happens very rarely, reducing opportunity for research. This also limit the scope for generalised findings to other similar situations.
Participants may not be randomly allocated to experimental conditions. Participants might be less sure whether IV has manipulated DV.
Lack of control – natural experiments have no control over the environment & other extraneous variables which means that the researcher cannot always accurately assess the effects of the I.V, so it has low internal validity.
Not replicable – due to the researcher’s lack of control, research procedures cannot be repeated so that the reliability of results cannot be checked.
Quasi experiments
Have an IV that is based on an existing difference between people eg age or gender. No one has manipulated the variable. IV cannot be changed.
As with a natural experiment the DV may be naturally occurring eg exam results or maybe devised by the experimenter and measured in the field or lab.
Strengths and limitations of quasi-experiments
Often carried out under controlled conditions and therefore share some strengths with a lab experiment eg replication
Can’t randomly allocate participants to conditions and therefore may be confounding variables.
IV is not deliberately changed by researcher and therefore we cannot claim that the IV has caused any observable change.
