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The GENMOD Procedure |

**VARIANCE***variable = expression***;**

You can specify a probability distribution
other than the built-in distributions by
using the VARIANCE and DEVIANCE statements.
The variable name *variable* identifies
the variance function to the procedure.
The *expression* is used to define the functional
dependence on the mean, and it can be any arithmetic
expression supported by the DATA step language.
You use the automatic variable _MEAN_
to represent the mean in the expression.

Alternatively, you can define the variance function with programming statements, as detailed in the section "Programming Statements". This form is convenient for using complex statements such as if-then-else clauses. Derivatives of the variance function for use during optimization are computed automatically. The DEVIANCE statement must also appear when the VARIANCE statement is used to define the variance function.

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