Comparative Nonrandom Pretest-Posttest Experiment

See: Comparative Random Pretest-Posttest Experiment, Posttest-Only Comparative Experiment.

References

(Henning & Henning, 2006) ⇒ Gavin Henning, and Terri Henning. (2006). “Experimental Designs."
- Two groups, Nonrandom Selection, Pre-test, Post-test: The main weakness of this research design is the internal validity is questioned from the interaction between such variables as selection and maturation or selection and testing. In the absence of randomization, the possibility always exists that some critical difference, not reflected in the pretest, is operating to contaminate the posttest data. For example, if the experimental group consists of volunteers, they may be more highly motivated, or if they happen to have a different experience background that affects how they interact with the experimental treatment - such factors rather than X by itself, may account for the differences.