Types of investigation

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Psychology unit 4 research methods revision
Types of investigation
Lab experiment: an experiment is where 2 groups are compared to see if there is a
difference. The IV is altered directly by the experimenter. All other extraneous
variables are tightly controlled. The DV is observed and recorded.
+high internal validity- all extraneous variables are tightly controlled so cause and
effect relationships can be determined
-low ecological validity- can't generalise results to real life
Field experiment: comparing 2 groups to see if there is a difference which takes
place in a real life setting
+high ecological validity- represents what happens in real life
-low internal validity- hard to control extraneous variables so cause and effect
relationships can't be determined
Natural experiment: the IV isn't altered by the experimenter but by another
force of nature. Extraneous variables are controlled but the extent to which is
determined by the environment the experiment is conducted in.
+if groups are tested in natural settings then the study has good ecological
validity but if the groups are tested in artificial settings them they have poor
ecological validity
-groups can be biased as they aren't randomly allocated so valid conclusions can't
be made
Correlation: 2 DV's are investigated to see if there is a link
+allows the investigation of areas in which an experiment would be unethical
-can't establish cause and effect so whilst we know there is a link we won't know if
the link is the actual cause
Self report measures: questionnaire (open/closed questions or likert scale),
interviews (structured/unstructured questions)
+interviews: participants can check to make sure they understand the question
which can also be changed to suit different abilities
+questionnaires: quicker than interviews so can get a larger sample of results and
therefore better population validity
-social desirability bias (when people lie to fit in with societies expectations)
leads to poor internal validity so answers can be untruthful

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Psychology unit 4 research methods revision
Case study: small group of participants that are studied in high amounts of detail.
These are usually longitudinal studies which are when the study occurs over a long
period of time.…read more


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