**Syntax**

` >>>> RANGE: lower upper`

or

`>>>> BOUND (LINEAR):`

*lower upper***Parent Command**

all third-level commands in block ` > PARMETER
`

**Subcommand**

` -`

**Description**

This command sets the admissible parameter range. It provides lower and upper bounds of the parameter. During the optimization process, iTOUGH2 may suggest parameter values that are physically not valid (e.g. negative porosity) or not reasonable (e.g. very high permeability). Limiting the admissible range for the values a parameter can assume prevents the simulation from stopping due to an unphysical or unreasonable parameter value. However, it is strongly suggested not to specify a narrow parameter range about the initial guess. The range should reflect physical bounds, and the expected variation of the parameter. If prior knowledge suggests that a certain parameter varies only slightly about the initial guess, this information should enter the inversion as a standard deviation associated with the initial guess, i.e., prior information (see command `>>>> DEVIATION` (p)). A parameter tends to greatly vary, potentially hitting its lower or upper bound, if (i) a systematic error is present, (ii) the initial guess is far away from the best estimate, (iii) the parameter is not sensitive, or (iv) the parameter is highly correlated to more sensitive parameters. The final parameter set should not contain parameters at their lower or upper bounds. If some of the estimated parameters are at the bounds, it is suggested to carefully examine the four potential reasons mentioned above. A new inversion should be performed after corrective actions have been taken. Use keyword `LINEAR` to provide the range of a parameter in linear scale even if the logarithm of the parameter is to be estimated.

**Example**

` > PARAMETER
>> POROSITY
>>> MATERIAL: SANDY
>>>> PRIOR information : 0.34
>>>> standard DEVIATION: 0.05
>>>> admissible RANGE : 0.01 0.99
<<<<
<<<
<<`

**See Also**

` >>>> DEVIATION (p) | >>>> STEP (p)
`