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Critical Path Method

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The Critical Path Method (CPM) is a fundamental project scheduling technique used to determine the sequence of activities that directly affects the project's completion time. In the context of activity definition and sequencing, CPM helps project managers identify the longest path of dependent activities (the critical path) through the project's schedule network diagram. This critical path represents the shortest possible project duration, as any delay in the activities along this path will directly impact the project's end date. CPM involves mapping out all the project's activities, estimating their durations, and defining their dependencies. By calculating the earliest and latest possible start and finish times for each activity, project managers can determine the total float or slack for non-critical activities. Float indicates how much an activity can be delayed without affecting the overall project timeline. Understanding the critical path and float allows for better resource allocation and risk management. Using CPM, project managers can focus their attention on the critical activities that have no flexibility in their schedule, ensuring that these tasks are carefully monitored and completed on time. It also aids in exploring schedule optimization opportunities, such as schedule compression techniques like fast-tracking or crashing, to meet project deadlines. Moreover, CPM provides valuable insights during the planning phase by highlighting potential bottlenecks and enabling proactive adjustment of activity sequences. It enhances communication among stakeholders by providing a clear visualization of the project's schedule and critical activities. Overall, the Critical Path Method is an essential tool in activity sequencing, facilitating efficient project planning, scheduling, and timely project completion.

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PMI-SP - Activity Definition and Sequencing Example Questions

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Question 1

In a critical path analysis, which of these calculations best describes the Total Float of a non-critical activity?

Correct Answer: Latest Start Time minus Earliest Start Time

Total Float (also known as Total Slack) in critical path analysis is the amount of time an activity can be delayed before causing a delay to the project completion date. The correct calculation for Total Float is: Latest Start Time (LST) minus Earliest Start Time (EST). This represents the maximum amount of time an activity can be delayed from its earliest start time before it affects the project end date. Alternative answers are incorrect because: - Adding delays between dependencies would result in an incorrect cumulative value - The difference between duration and remaining work is a progress metric, not a float calculation - Adding LST and EST of successors would produce an invalid numerical value that does not represent available scheduling flexibility

Question 2

In Critical Path Method (CPM), what is the primary purpose of total float in relation to resource management?

Correct Answer: It indicates how long an activity can be delayed before impacting the project end date

Total float in CPM is the amount of time an activity can be delayed from its early start date before it delays the project completion date. This is the primary function of total float in resource management as it helps project managers understand the flexibility they have in scheduling activities and allocating resources while maintaining the project end date. The other answers are incorrect because: The idea that total float represents maximum duration for allocating additional resources is inaccurate - total float is about timing flexibility, not resource allocation capacity. Total float is not specifically designed to show time needed for resource leveling across parallel activities. While it may help in resource planning, this is not its primary purpose. Total float does not measure resource buffers between dependent activities. It measures schedule flexibility, not resource availability between activities.

Question 3

According to Critical Path Method (CPM), what happens when a task on the critical path has both positive total float and positive free float?

Correct Answer: This scenario is impossible as critical path tasks always have zero float

In Critical Path Method (CPM), the critical path is defined as the sequence of activities that determines the shortest time to complete the project. By definition, tasks on the critical path have zero total float and zero free float. This is a fundamental principle of CPM because: 1. Critical path activities determine the project duration 2. Any delay in a critical path activity will delay the entire project 3. Float (both total and free) represents scheduling flexibility 4. Having float means the activity can be delayed that amount of time before impacting the project end date Therefore, it is mathematically impossible for an activity to be on the critical path AND have any type of float (positive total float or positive free float). If an activity has float, it is by definition not on the critical path. The other answers suggest various actions or remedies, but they are not relevant since the premise of the question describes an impossible scenario in CPM scheduling.

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