Activity Network Diagram(AND) - Scheduling sequential & simultaneous tasks : PART II

How do I do it?

1. Assemble the right team of people with first and knowledge of the subtasks.

2. Brainstorm or document all the tasks needed to complete a project. Record on Post-its™.

3. Find the first task that must be done, and place the card on the extreme left of a large work surface

4. Ask: "Are there any tasks that can be done simultaneously with task#1?"

• If there are simultaneous tasks, place the task card above or below task#1. It not, go to the next step.

5. Ask, "What is the next task that must be done? Can others be done simultaneously?"

• Repeat this questioning process until all the recorded tasks are placed in sequence and in parallel.

Tip At each step always ask, "Have we forgotten any other needed tasks that could be done simultaneously?"

6. Number each task, draw the connecting arrows, and agree on a realistic time for the completion of each task.

• Record the completion time on the bottom half of each card.

Tip Be sure to agree on the standard time unit for each task, e.g., days, weeks. Elapsed time is easier than "dedicated" time, e.g., 8 hours of dedicated time versus 8 hours over a two-week period(elapsed time).

7. Determine the project's critical path

• Any delay to a task on the critical path will be added to the project's completion time, unless another task is accelerated or eliminated. Likewise, the project's completion time can be reduced by accelerating any task on the critical path.
• There are two options for calculating the total critical path and the tasks included within it. 

Longest cumulative path. Identity total project completion time. Add up each path of connected activities. The longest cumulative path is the quickest possible implementation time. This is the project's critical path.


Calculated slack. Calculate the "slack" in the starting and completion times of each task. This identifies which tasks must be completed exactly as scheduled (on the critical path) and those that have some latitude.

Finding the critical path by calculating the slack

Tip Determining the longest cumulative path is simpler than calculating the slack, but can quickly become confusing in larger ANDs

The calculated slack option determines the total project and slack times; and therefore the total project time and critical path are identified" automatically."

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