SOAN 3120 Chapter Notes - Chapter 9: Random Assignment, Dependent And Independent Variables, Design Of Experiments
22 Oct 2016
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An observational study observes individuals and measures variables of interest, but does not attempt to influence the responses: the purpose of an observational study is to describe some group or situation. This distinction is one of the most important in statistics. A study is an experiment when we actually do something to people, animals, or objects to observe the response. The individuals studied in an experiment are often called subjects, particularly when they are people. A treatment is any specific experimental condition applied to the subjects. If an experiment has more than one factor, a treatment is a combination of specific values of each factor. An advantage of experiments is that we can study the combined effects of several factors simultaneously. Outside the laboratory, uncontrolled experiments often yield worthless results because of confounding with lurking variables. I. e. , field experiments and experiments with living subjects are exposed to more variable conditions and deal with more variable subjects.
