**Syntax**

` >>>> VARIATION: sigma`

**Parent Command**

all third-level commands in block` > PARAMETER
`

**Subcommand**

` -
`

**Description**

This command specifies the expected variation *sigma* of a parameter p. *sigma* is used to scale the columns of the Jacobian matrix, yielding dimensionless and comparable sensitivity coefficients. While the solution of the inverse problem is not affected by the choice of the scaling factor, all the qualitative sensitivity measures are directly proportional to *sigma*:

scaled sensitivity coefficient:

If no standard deviation (see `>>>> DEVIATION` (p)) or parameter variation is specified, the scaling factor is taken to be 10 % of the respective parameter value. For sensitivity analyses, *sigma* can be taken as the perturbation one would apply to study the effect of the parameter on the modeling result.

As `>>>> VARIATION` indicates that no prior information is available, the data-worth analysis will examine the value of adding such information.

**Example**

` > PARAMETER
>> POROSITY
>>> MATERIAL: FAULT
>>>> expected VARIATION : 0.10
<<<<
<<<
>> ABSOLUTE permeability
>>> MATERIAL: FAULT
>>>> expected VARIATION : 1.00 (one order of magnitude)
<<<<
<<<
<<`

> COMPUTATION

>> OPTION

>>> SENSITIVITY analysis

<<<

<<

**See Also**

` >>>> DEVIATION (p) | >>> WORTH (op)
`