Quasi-Experiments Flashcards
How does a Quasi experiment differ from a true experiment?
in a true experiment you can randomly assign participants whereas a Quassi experiment you cannot
What would be some areas of research that a Quassi experiment would be used?
research on:
- gun control
- road safety
- exposure to air pollution
- exposure to harsh chemicals
Quasi=
“almost”
so an “almost” experiment
What is a pretest-posttest design?
Compare level of DV before and after change in IV
what are the problems for the internal validity of one-group pretest-posttest quasi-experiment?
Changes might be due to:
- history
- regression to mean
- maturation
- mortality (attrition)
- testing/sensitization
History (pretest-posttest)
- other events might be happening in the meantime
Regression to mean (pretest-posttest)
if group is selected for extreme values, they will tend to be less extreme when next measured
Maturation (pretest-posttest)
any development, including aging
Mortality “attrition”(pretest-posttest)
people who “drop out” might differ from those who don’t
Testing/sensitization (pretest-posttest)
being measured or observed once might lead to changes next time
What is a two-group posttest-only design?
Compare DV in two groups after one receives IV and other doesn’t
what are the problems for the internal validity of a two-group posttest only?
changes might be due to:
- selection
- selection-by-history interaction
Selection (two-group posttest)
pre-existing differences between groups - no random assignment
selection-by-history interaction (two-group posttest)
things that have happened/are happening to one group and not the other
How can we fix the problems that are cuased my a two-group posttest design?
use a Two group pretest-posttest design instead
