Page 152 - Project+

FIGURE 5.5 Gantt chart

Network diagrams can also be used to display the project schedule if you add dates and
durations in the boxes on the diagram.

The Critical Path Method

One of the most widely used techniques in schedule development is the critical path
method (CPM). CPM determines the amount of float time for each activity on the
schedule by calculating the earliest start date, earliest finish date, latest start date, and
latest finish date for each task. Float is the amount of time you can delay the earliest
start of an activity without delaying the ending of the project. Tasks with the same
early and late start dates and the same early and late finish dates have zero float and

are considered critical path tasks. If a critical path task does not finish as scheduled,
the project end date will be affected.

For the exam, remember that tasks with zero float are critical path tasks.
It is possible to calculate float time manually, but the formulas are beyond the
scope of this book and the exam. Float time calculations are easily performed in

project-scheduling software.

The critical path is the longest full path on the project. If you refer to Figure 5.2, you’ll
see that the longest path for this project has a duration of 20 days. This is calculated by

adding the durations for the A-B-D path (Task A, Task B, and Task D). Simply add up
the task durations for that path.

Table 5.2 shows the start and end dates and durations for the project tasks in table
form. When calculating the start and end dates, the first day counts as day 1. Task A
starts on 10/6, and it’s worked on all day on the 6th, 7th, and 8th because it has a
duration of three days. The next task can start on the 9th. In this example, there are no
holidays or vacation days.

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