Critical path analysis

Summary

This video script outlines the process of using Critical Path Analysis (CPA) for project planning. CPA involves creating network diagrams with nodes and arrows to map tasks, their order, and durations. The script uses a cooking breakfast example to illustrate how to construct a network diagram, calculate earliest start times, latest finish times, and identify the critical path with no leeway for delay. It emphasizes the importance of prioritizing critical path activities and managing float time, while acknowledging the reliance on accurate timing estimates and the potential for unexpected events.

Takeaways

• 📋 Critical Path Analysis (CPA) is a project planning technique using network diagrams to map tasks and their sequence.
• 🔄 In network diagrams, nodes represent the start or end of activities, with the earliest start time (EST) in the top right and the latest finish time (LFT) in the bottom right.
• ➡️ Arrows indicate tasks with their durations, showing the flow and order of activities within the project.
• 🍳 In the example provided, a network diagram is used to plan a breakfast, detailing tasks like preparing ingredients, cooking, and serving.
• 🕒 EST is calculated by summing the durations of activities on the longest path, while LFT is determined by working backward from the project’s end time.
• ❌ The critical path includes tasks that cannot be delayed without impacting the project timeline; delaying them would extend the overall project duration.
• ⏳ Tasks not on the critical path have 'float time'—the leeway available without affecting the project’s finish time.
• 🔍 Float time is calculated by subtracting the task's duration and EST from its LFT, showing how much a task can be delayed.
• 🛠️ CPA helps prioritize tasks that need attention to stay on schedule, especially those on the critical path with zero float time.
• ⚠️ CPA’s effectiveness depends on accurate time estimates and is sensitive to unexpected events, underscoring the need for skilled planning.

Q & A

What is critical path analysis (CPA)?

Critical path analysis (CPA) is a project planning technique that uses network diagrams to map out tasks, showing the order in which they need to be completed, the earliest start times, and the latest finish times for each task.

What symbols are used in network diagrams for CPA?

In CPA network diagrams, circles (nodes) are used to represent the start or end of an activity. Arrows indicate the tasks or activities to be completed, with the duration of each activity written next to the arrow.

What do 'EST' and 'LFT' represent in a node?

'EST' (Earliest Start Time) is the earliest time an activity can begin, based on the completion of prerequisite activities. 'LFT' (Latest Finish Time) is the latest time an activity must be completed to keep the project on schedule.

How do you determine the earliest start time (EST) in a network diagram?

The earliest start time (EST) is calculated by adding the duration of the preceding activity to the EST of the previous node. This process continues until the last node is reached.

How do you calculate the latest finish time (LFT) in a network diagram?

The latest finish time (LFT) is calculated by working backward from the final node, subtracting the duration of each activity from the LFT of the subsequent node.

What is the critical path in CPA?

The critical path is the sequence of activities that cannot be delayed without affecting the overall project completion time. These tasks have no float time, meaning any delay will extend the total project duration.

What is float time, and how is it calculated?

Float time is the amount of time an activity can be delayed without delaying the project. It is calculated by subtracting the duration of the activity and its earliest start time from the latest finish time.

What is an example of calculating total float for an activity?

For example, if the latest finish time for an activity is 30 minutes, the activity duration is 5 minutes, and the earliest start time is 15 minutes, the total float would be 10 minutes (30 - 5 - 15 = 10).

What is the main advantage of using critical path analysis?

The main advantage of CPA is that it helps prioritize critical activities that must be completed on time to keep the project on schedule, allowing managers to allocate resources effectively.

What are some disadvantages of critical path analysis?

Disadvantages include its reliance on accurate time estimates for each activity. If the estimates are incorrect or unexpected events occur, the CPA becomes less effective. Additionally, the effectiveness of CPA depends on the experience and skill of the person preparing the network.