Biology 2244A/B Chapter Notes - Chapter 8: Design Of Experiments, Random Assignment, Observational Error
16 Sep 2016
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Individuals in an experiment are called subjects when they are people and experimental units otherwise. Explanatory variables (independent variables) are often called factors. A treatment is any specific experimental condition applied to the subjects. If subject has more than one factor, a treatment is a combination of specific values of each factor. Most well-known experiments compare two or more treatments. Part of the design of an experiment is a description of the factors (explanatory variables) and the layout of the treatments, with comparison as the leading principle. If the treatments are given to groups that differ markedly when the experiment begins, bias will result. Experimental group group of individuals receiving treatment whose effect we seek to understand. Control group serves as a baseline with which the experimental group is compared. Placebo is control treatment that is face but otherwise indistinguishable from the treatment in the experimental group.
