Intro to Project Management: Project Schedule Management - Critical Path Method, CPM Identifying Critical Path Float Near-Critical Path

What This Is

The Critical Path Method (CPM) is a project management technique used to identify the longest sequence of dependent tasks that determines the minimum duration required to complete a project. This method helps project managers understand which tasks are critical to the project's timeline and which tasks have some flexibility in terms of scheduling. For example, consider building a bridge: the critical path might be the sequence of tasks related to constructing the bridge's foundation, followed by the installation of the bridge's superstructure, and finally, the completion of the bridge's finishing work.

Key Terms & Formulas

• Critical Path: The longest sequence of dependent tasks that determines the minimum duration required to complete a project.
• Critical Path Length (CPL): The total duration of the critical path tasks.
• Float (or Slack): The amount of time a task can be delayed without affecting the project's completion date.
• Near-Critical Path: A path that has a duration very close to the critical path and can become critical if any task on the critical path is delayed.
• Early Start (ES): The earliest possible start time for a task, considering the dependencies and the task's duration.
• Early Finish (EF): The earliest possible finish time for a task, considering the dependencies and the task's duration.
• Late Start (LS): The latest possible start time for a task, considering the dependencies and the task's duration.
• Late Finish (LF): The latest possible finish time for a task, considering the dependencies and the task's duration.
• Critical Path Method (CPM) Formula: CPM = ES + Duration
• Float Formula: Float = LF - EF
• Near-Critical Path Formula: Near-Critical Path = CPL - (CPL x Float)

Step-by-Step / Process Flow

1. Create a Project Schedule: Develop a detailed project schedule using the project management methodology of your choice (e.g., Gantt chart, PERT chart).
2. Identify Dependencies: Determine the dependencies between tasks and identify the critical path.
3. Calculate Early and Late Dates: Calculate the early start, early finish, late start, and late finish dates for each task.
4. Identify Critical and Near-Critical Paths: Identify the critical path and near-critical paths based on the calculated dates.
5. Analyze Float: Analyze the float for each task to determine which tasks have flexibility in terms of scheduling.
6. Develop a Project Schedule Risk Plan: Develop a plan to manage risks associated with the critical and near-critical paths.

Common Mistakes

• Mistake: Assuming that all tasks on the critical path are equally critical.
• Correction: Identify the most critical tasks on the critical path and focus on managing those tasks first.
• Mistake: Failing to consider near-critical paths when developing a project schedule risk plan.
• Correction: Include near-critical paths in the risk plan to ensure that the project can adapt to changes in the critical path.
• Mistake: Not calculating float for each task.
• Correction: Calculate float for each task to determine which tasks have flexibility in terms of scheduling.

Exam Tips

• Tip: Be prepared to calculate critical path length, float, and near-critical path.
• Tip: Understand the difference between critical and near-critical paths.
• Tip: Be able to explain the importance of float in project scheduling.

Quick Practice Questions

1. If the CPI is 0.8, is the project under or over budget? Answer: Over budget. Explanation: CPI (Cost Performance Index) is the ratio of Earned Value to Actual Cost. A CPI of 0.8 indicates that the project is spending more than planned.
2. What is the formula for calculating float? Answer: Float = LF - EF. Explanation: Float is the amount of time a task can be delayed without affecting the project's completion date.
3. If a task has a duration of 5 days and a late finish date of 10 days, what is its float? Answer: 5 days. Explanation: Float = LF - EF = 10 - 5 = 5 days.

Last-Minute Cram Sheet

• Critical Path: The longest sequence of dependent tasks that determines the minimum duration required to complete a project.
• Critical Path Length (CPL): The total duration of the critical path tasks.
• Float (or Slack): The amount of time a task can be delayed without affecting the project's completion date.
• Near-Critical Path: A path that has a duration very close to the critical path and can become critical if any task on the critical path is delayed.
• Early Start (ES): The earliest possible start time for a task, considering the dependencies and the task's duration.
• Early Finish (EF): The earliest possible finish time for a task, considering the dependencies and the task's duration.
• Late Start (LS): The latest possible start time for a task, considering the dependencies and the task's duration.
• Late Finish (LF): The latest possible finish time for a task, considering the dependencies and the task's duration.
• CPM Formula: CPM = ES + Duration.
• Float Formula: Float = LF - EF.
• Near-Critical Path Formula: Near-Critical Path = CPL - (CPL x Float).
• Float is not the same as slack.