In a quasi experiment, one follows all the guidelines of an experimental research except that there is no random selection of objects of study. The researcher does not observe fundamental rules of natural probability. A quasi experiment is not a randomized trial. An example of an impossible quasi-experiment is a trial to evaluate the effects of treatment of a certain type of cancerous tumor using a particular drug undergoing viability test. Since cancer is a disease and a naturally occurring ailment for that matter, a scientist is no able to assign the cancerous growths to random patients. This situation is an example of an impractical situation. However, the scientist can gather a group of patients with the particular type of cancer, and subject them to a treatment regime using the drug. The scientist can then assess the condition of each patient, and enumerate the number of patients with varied degrees of positive response. Eventually, the scientist determines the success of the drug exclusively among cancer patients, but not among the human population.
In other cases, the process of randomization might be unethical and thus the researcher avoids it. In a case involving a school, it is unethical to assign different teaching methods to students of the same age and level. However, if the school administration wishes to determine the best teaching method for a certain level, say, the third form, the researchers will have to subject all the third formers in a class to a certain teaching method. The performance of the class is thus evaluated as a whole. This presents a quasi experiment since all the students are subjected to the same conditions. It is unethical to divide the students into several groups and subject them to different teaching methods. This is because some of the groups may be disadvantaged by an ineffective method of teaching, leading to poor performance. However, the school administration is able to know the effect of the particular method on all students.