  Project managers need to manage risks throughout the project lifecycle and,
thus, need to know how changes in activity durations influence project duration
and risk. We propose a new indicator (the Activity Risk Index, ARI) that
measures the contribution of each activity to the total project risk while it
is underway. In particular, the indicator informs us about what activities
contribute the most to the project's uncertainty so that project managers can
pay closer attention to the performance of these activities. The main
difference between our indicator and other activity sensitivity metrics in the
literature (e.g. cruciality, criticality, significance, or schedule sensitivity
indices) is that our indicator is based on the Schedule Risk Baseline concept
instead of on cost or schedule baselines. The new metric not only provides
information at the beginning of the project, but also while it is underway.
Furthermore, the ARI is the only one to offer a normalized result: if we add
its value for each activity, the total sum is 100%.
