For those risks you accept, because you either choose not to develop a response or can't further mitigate their probability or impact, you can set aside contingency reserve to address the event when and if it occurs. No prescribed equation can determine the appropriate amount of reserve to set aside; every project is different. Here's a list of factors that generally indicate you should set aside more reserve:
- New or unproven technology
- Complex projects with numerous interfaces
- Projects that are unfamiliar to your organization
- Resources unfamiliar with the type of work to be done
- A constrained budget
- Business-critical or high-profile project
The figure shows how a task called Registration Contingency was added to reduce the probability that a slip on any task in the Registration work packages would delay the Registration Available milestone. If everything goes as planned, then the contingency won't be used. However, if there are tasks that need to be reworked, or if there are problems with a resource, or if a stakeholder isn't available for feedback, there is some reserve built in.
Set aside contingency reserve for both the schedule and the budget.