Random Assignment

Random assignment is the process by which researchers select individuals from their total [Page 1194]sample to participate in a specific condition or group, such that each participant has a specifiable probability of being assigned to each of the groups or conditions. These different conditions or groups represent different levels of the independent variable. Random assignment is generally considered the most important criterion to qualify a research design as an experimental design. A common example of random assignment is a medical trial in which a researcher assigns some participants at random to receive either a treatment drug or a placebo (a pill that looks like the medication but is known to be inert). Because of the random assignment, any differences that are observed in the outcome ...