Dr.Kalmagura plans on introducing a new exam review procedure in his chemistry classes.To check the effectiveness of the new procedure,he is going to have half his students try the new technique for one semester,while the remaining students review in the way they have always done in the past.He asks each student to decide whether they would like to use the new technique or the standard technique.What procedure is illustrated in this example

A)  a double-blind research design 
B)  informed consent in research 
C)  the use of non-random assignment 
D)  naturalistic observation

This is an example of non-random assignment because the students are given the choice of which review technique they would like to use. The assignment to the new technique or standard technique is not random, but rather self-selected by the students. This could potentially introduce bias into the study. A double-blind research design involves neither the experimenter nor the participants knowing which group they are in, and informed consent is a procedure used to obtain ethical approval from participants in research. Naturalistic observation involves observing behavior in a natural setting without any intervention or manipulation by the researcher. None of these procedures apply to this example.