1 For example, the disorder sickle cell anaemia is caused by a mutation in the gene that instructs the building of a protein called haemoglobin. 2  This causes the red blood cells to become an abnormal, rigid, sickle shape. 3  However, in African populations, having this mutation also protects against malaria.
Optimistic time - generally the shortest time in which the activity can be completed. It is common practice to specify optimistic times to be three standard deviations from the mean so that there is approximately a 1% chance that the activity will be completed within the optimistic time.
Let us assume that a project can be broken down into activities A, B, C and D. The Critical Path runs along A, B and D and task C is parallel to sub-activity D. In this scenario if task B stretches beyond its estimated duration by X hours, then by default activity D should be completed X hours ahead of time. Unless this happens, the project will veer from its proposed timeline.