Some Additional Remarks Concerning the Subject Time

  • Three point estimatings are methods to find a probably more valid value by estimating three values and computing one on this base - instead of estimating the one value directly (comp. PMBOK3, p. 142). These methodes are operating on different concepts:
    • Build average :- (Optimistic-Value + Most-Likely-Value + Pessimistic-Value)/3
    • Pert formular :- (Optimistic-Value + (4*Most-Likely-Value) + Pessimistic-Value)/6
    • Standard Deviation :- (Pessimistic Value - Optimistic Value)/6
    • Variance :- ((Pessimistic Value - Optimistic Value)/6)^2
  • Earned Value Technique takes the planned costs for realizing a task as target and defines a scale, which announces how much of the task must already be fullfilled for having earned how much of the costs. Then one can report the earned value progress of a task.
  • The Forward Pass is a method to expand the logical structure of a net of tasks - created by Activity Sequencing - to a net of possible durances. This is realized by executing the following steps:
    • Take the early finish date of the predecessor as early start of his successors.
    • Compute the early finish date of each of these successors by adding their specific duration time to the early start date.
    • Do the same for all successors of the successor.
    • Integrate defined lags and leads, given by the activity attributes
  • The Backward Pass is the 'opposite' of the Forward Pass:
    • Compute the latest start date of the successor by subtracting the duration time from the latest finish date.
    • Take the latest start date of the sucessor as latest finish date of all his predecessors.
    • Do the same for all predecessors (and their predecessors).
    • Integrate defined lags and leads, given by the activity attributes
  • Free Float - also known as Slack - is the time an activity can be delayed without delaying the project finish date.
  • GERT - also known as Graphical Evaluation and Review Technique - is special network diagramming method which can not only integrate what-if-szenarios but also loops: in this case the diagram can also be a directed cyclic graph, not only a directed acyclic graph.