Fr. Dominic, the bread monk, demonstrates how to tell if a loaf is fully baked using three different methods: baking time, gently tapping the crust of the loaf, and using a thermometer. Transcript: Hi, I'm Father Dominic the Bread Monk, author of How to Be a Breadhead and this is a Breadhead Minute.
The difference is that in a quasi-experiment the criterion for assignment is selected by the researcher, while in a natural experiment the assignment occurs 'naturally,' without the researcher's intervention. Quasi experiments have outcome measures, treatments, and experimental units, but do not use random assignment.
The posttest-only randomized experimental design is, despite its simple structure, one of the best research designs for assessing cause-effect relationships. It is easy to execute and, because it uses only a posttest, is relatively inexpensive. But there are many variations on this simple experimental design.