Reactive effects of experimental arrangements , which would preclude generalization about the effect of the experimental variable upon persons being exposed to it in nonexperimental settings. Multiple-treatment interference , likely to occur whenever multiple treatments are applied to the same respondents, because the effects of prior treatment are not usually erasable. You may not be able to distinguish which treatment worked. Ethical Issues in Experimental Research 1.Deception occurs when subjects are misled about research procedures to determine how they would react to the treatment if they were not research subjects. Researchers must weigh the potential harm to subjects and debrief those who have been deceived.
Random assignment is the fairest way to distribute a treatment.