Unit 10: Quasi Experimentation Flashcards
quasi experiments
The researcher selects participants from pre-existing groups (does not have control over assigning subjects to conditions).
Sometimes called ex post facto because assignment happens after the groups have formed (ex. male/female)
Difference between groups may not be the cause of the effect, could be obscuring the effect.
non-equivalent control group designs
Experiment with a control and experimental group, but P are nor randomly assigned to them.
repeated treatment designs
A design that attempts to improve validity by introducing the treatment more than once (return to baseline in between).
interrupted time-series designs
A design that considers the trend before and after the experiment, so one group can be tested alone (no control)
program evaluation
A set of techniques for determining the effectiveness of a social service program.
summative evaluation
A way to determine whether a program is functioning adequately, meeting its goals.
Often after completion.
Can be used to determine cutbacks, changes, expanding, etc.
formative evaluation
The goal is to improve the program.
cross-sectional study
A design that tests different age groups at the same time to determine age-based differences.
longitudinal study
A design that follows one P/group and tests them at different points over time to determine age-based differences.
cross-sequential design
Tests 2+ groups at 2+ times to control for cohort effects, secular effects.
Cohort effect
Effects of characteristics that are specific to a cohort.
secular effect
Effects due to changes in the larger population/social environment.
How are quasi experiments different from true experiments?
Still intend to show cause-effect, but one of these is not met:
- researcher randomly assigns P to 2 groups that are roughly equivalent
- researcher manipulates the IV
- there is a control or baseline condition to compare to experimental/treatment condition
Under what circumstances can quasi experiments be a useful tool?
- when only option/better than nothing
- when can’t practically or ethically assign P to groups for exposure to the IV
- can test lab results for external validity
- can suggest further research for lab
- can have higher external validity than true if more closely resembles the real world
What is the major weakness of quasi experiments?
Confounding variables. Because the researcher doesn’t have complete control over assigning P to conditions. Difference between groups could be the cause of effect, or could be obscuring the real cause.