Parent Command
>> ERROR

Subcommand
-

Description
The estimated error variance s02 represents the variance of the mean weighted residual and is thus a measure of goodness-of-fit:

The a posteriori error variance so2 or a priori error variance sigma₀² is used in the subsequent error analysis. For example, the covariance matrix of the estimated parameters, C_pp, is directly proportional to the scalar s₀² or sigma₀², respectively. Note that if the residuals are consistent with the distributional assumption about the measurement errors (i.e., matrix C_zz), then the estimated error variance s₀² assumes a value close to one. The user must decide whether the error analysis should be based on the a posteriori or a priori error variance. The decision can also be delegated to the Fisher Model Test (see command >>> FISHER). iTOUGH2 uses the a posteriori error variance s₀² by default. However, for design calculations or synthetic inversions, the error analysis should be based on the a priori variance sigma₀² which is 1 by definition.

Example
> COMPUTATION
>> ERROR
>>> based on A PRIORI error variance
<<<

See Also
>>> FISHER | >>> POSTERIORI