6.1.14 (HL)—Critical path analysis

Critical path analysis identifies the longest dependent sequence of project activities and the minimum completion time.

A delay on a critical activity delays the project unless resources or sequencing change; non-critical tasks have slack.

List durations/dependencies, find earliest/latest times and focus control on zero-slack work.

If A→B→C takes 3+4+5 days, that path takes 12 days and is critical unless another path is longer.

The critical path can change when durations or dependencies change.

Complete a supplied network by moving forward to calculate earliest start times and project duration, then backward to calculate latest finish times. Total float = latest finish time − earliest start time − activity duration; activities with zero total float form a critical path. Free float = earliest start time of the next activity − earliest start time of the current activity − duration, using the earliest relevant following start when there is more than one successor. If an activity starts earliest at day 3, lasts 4 days and may finish latest at day 9, total float is 9 − 3 − 4 = 2 days. Drawing the diagram is not expected, but completing and analysing the provided diagram is; a changed duration can change the critical path.