What are dummy variables


Dummy variable


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Has a variable a few "characteristics", then they are referred to as "categorical variables". Assume this variable has a total of Characteristics (categories). For some statistical evaluations it is helpful to know whether a unit of investigation is one of these Has characteristics or not. For this purpose, a so-called proxy variable is created (English: dummy variable) with the values ​​1 and 0: a 1/0 coded Dummy variable. in the case of an examination unit means that the examination unit has the characteristic of interest. means that it has a different expression. In the same way, you can create dummy variables for the other forms of form. At total Characteristics are in principle Dummies conceivable: . However, one can easily consider that one is merely Dummies needed to do the To map expressions completely: Does an investigation unit have the characteristic , then you can tell by the fact that all Dummies have the value 0: .
HJA 2001-10-01