Presentation on theme: "D1: Critical Events And Critical Paths. D1: Critical Events And Paths A critical path is the list of activities on an activity network that, if they are."— Presentation transcript:
D1: Critical Events And Critical Paths
D1: Critical Events And Paths A critical path is the list of activities on an activity network that, if they are delayed, delays the entire project. A critical event is an event which cannot be delayed. A critical activity is an activity which cannot be delayed. To find critical activities, calculate the float: take the late event time at its head event and subtract both the early event time at its tail event and its duration. If an activity has a float of 0 it is a critical activity. Some events are not critical events. Non-critical events have a quantity called slack: it shows how much the event can be delayed without delaying the whole project.
The slack, s i, at an event i is calculated using s i = l i – e i So the slack at an event i is found by taking its early event time from its late event time. The slack at any critical event is 0, as this is an event that cannot be delayed! D1: Critical Events And Paths
The float, F(i, j), of an activity between events i and j is calculated using F(i, j) = l j – e i - a ij To calculate float, find the largest possible amount of free time you have to complete the activity (the difference between the latest event time at the head and the earliest event time at the tail). Subtract the activity duration from that. The float at any critical activity is 0, as this is an activity that cannot be delayed! D1: Critical Events And Paths