When entering an uncertain cost value, such as $1000 +10% / -5% you can enter the variance limits (+10% and -5%) manually. Alternatively, you can specify them in terms of a pre-defined confidence level. This will automatically insert pre-determined variance limits for you. In the example above, a confidence level of medium was used to insert the variance limits of +10% / -5%.
Unit prices can also be entered in the same way, using pre-defined confidence levels.
The lower the confidence level, the greater the variance limits. You can use confidence levels in both base+contingency and high/mid/low modes. (Base+contingency mode ignores the negative variance limit.)
Mandrel provides a default set of confidence levels and associated variances, and also lets you define your own set of levels and variances.
Changing the Confidence Level Definitions
If you decide to change the variance associated with a particular confidence level, it will not change the variances associated with any existing cost data. The confidence level system is used only to insert variances on data input, but is not directly linked to the data subsequently.