Contributory variance

The purpose of the development process is to determine the contributory variances to each of these three areas in order to minimise or control them. The instrument performance needs to be assured and this has been discussed in Chapter 5. Even if we assume initially that the operator contribution is small, we need to confirm that during this phase. Trust but verify ... 

The contributory variance required for model matching should be less than or equal to this expected tolerance, implying the p conditions ... 

Using the time-domain method described above, it is possible to calculate the time-behaviour of the modelmatching parameter variations, and hence it is a simple matter to determine the contributory variance (Soj) of each parameter that is necessary to match model to all the transient measurements recorded from the plant. To satisfy the explainability criterion, the variance of each parameter should be within the variance anticipated in advance, i.e. ... 

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