Statistical Sciences 1024A/B Chapter Notes - Chapter 9: Dependent And Independent Variables, Block Design, Graduate Management Admission Test
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20 Apr 2017
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I(cid:374) (cid:272)o(cid:374)trast to o(cid:271)ser(cid:448)atio(cid:374)al studies, e(cid:454)peri(cid:373)e(cid:374)ts do(cid:374)"t just observe individuals or ask them questions. They actively impose some treatment in order to measure the response. 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. An experiment, on the other hand, deliberately imposes some treatment on individuals to observe their responses. The purpose of an experiment is to study whether the treatment causes a change in the response. When our goal is to understand cause and effect, experiments are the only source of fully convicting data. Two variables (explanatory variables or lurking variables) are confounded when their effects on a response variable cannot be distinguished from each other. ** well-designed experiments take steps to avoid confounding** The individual studied in an experiment are often called subjects, particularly when they are people.