Quasi experimental designs

Quasi experimental designs - Quasi- Experimental Designs...

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Quasi- Experimental Designs (C. 12) Requirements for an experiment Independent variable (IV) o The IV must be under the control of the experimenter Experimenter varies the levels of IV and observes any changes in the DV o Experimenter must be able to assign subjects to the various levels of the IV o Examples: Anxiety, task difficulty, training program, medication dose Control Group Must possess the qualities of the experimental group except for the critical element that is the IV Assignment to Experimental and Control groups must insure that they are equivalent with regard to the DV prior to being treated differently Only with a true experiment can we determine cause and effect relationships Quasi-Experimental Designs A QED lacks one or both of the requirements for the experiment Sometimes you cannot match two groups/ have equivalent control group, etc Types o Demonstration (most common) Problem: no control; ex: put Tums in murky stomach acid & turns clear, but if no control condition, something else could turn it clear o Non-manipulated independent variable designs (textbook term)- this is not a true IV. It should be called a quasi-independent variable (e.g., subject variables) o Single group designs Single Group Post-Test Only No control group, don’t have baseline to compare it to (ex: implement new technology, measure change periodically after
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This note was uploaded on 02/21/2011 for the course PSY 418 taught by Professor Haley during the Spring '08 term at University of Texas at Austin.

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Quasi experimental designs - Quasi- Experimental Designs...

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