The Critical Path Method (CPM) can be used as a project management

Full Answer Section

1. he Impact on Subsequent Activities: The CPM network diagram illustrates the dependencies between activities. By analyzing the network, the project manager can see which activities are successors to the delayed non-critical activity.
2. The Available Slack: The CPM calculation provides the total slack time for the delayed activity and its subsequent non-critical path activities. This slack represents the buffer available before the delay impacts the critical path and the overall project completion date.

Recovery Strategies Using Slack Time:

The primary way CPM assists in recovering from non-critical path overruns is by absorbing the delay within the available slack. If the overrun of a non-critical activity is less than or equal to its total slack, the project completion date will not be affected. The project manager can monitor the progress of subsequent activities on that path to ensure they remain within their allocated time and don't further erode the slack.

However, if the overrun exceeds the total slack of that specific non-critical activity, it will start to impact the start times of its successor activities and potentially push the project completion date. In this scenario, CPM helps in:

• Identifying the Point of Impact: The CPM network highlights when the delay of the non-critical activity starts to impinge on the critical path or other non-critical paths with less remaining slack.
• Evaluating Trade-offs: Knowing the impact, the project manager can use the CPM to analyze potential trade-offs. For example, they might consider:
  • Reallocating Resources: Shifting resources (personnel, equipment) from non-critical activities with more remaining slack to the delayed non-critical activity to expedite its completion (if it's still ongoing) or its successors. This must be done carefully to ensure the activities from which resources are drawn do not then become critical.
  • Fast-Tracking: If the successors of the delayed non-critical activity are not sequentially dependent, some activities that were planned to be sequential could be performed in parallel to shorten the overall duration of that path. The CPM helps visualize these potential parallelization opportunities.
  • Crashing: If the delay significantly eats into the slack and threatens the critical path, the project manager might consider "crashing" certain activities (both on the affected non-critical path and potentially the critical path, though with more cost implications). Crashing involves adding more resources to shorten the duration of an activity, often at an increased cost. The CPM helps identify which activities, if crashed, would yield the most significant reduction in the overall schedule for the least cost.

Example:

Consider a simplified software development project with the following activities and durations (in days):

The critical path is A -> B -> D -> F, with a total duration of 5 + 3 + 6 + 3 = 17 days.

Activity C is not on the critical path and has a total slack of 2 days. Activity E, also not critical, has a total slack of 2 days.

Scenario: Activity C experiences a schedule overrun and takes 6 days to complete instead of the planned 4 days.

CPM Analysis for Recovery:

1. Delay: Activity C is delayed by 2 days (6 - 4 = 2 days).
2. Impact: Activity E, which depends on C, will now start 2 days later than planned.
3. Slack: Activity C had a total slack of 2 days. The 2-day delay entirely consumes this slack.
4. Current Status: The start of Activity E is now at day 5 + 6 = 11 (originally planned for day 5 + 4 = 9). Activity E still has its original duration of 5 days, finishing on day 16. Activity F, which also depends on D (finishing on day 5 + 3 + 6 = 14), can only start on the later of day 14 and day 16, which is day 16. Activity F will then finish on day 16 + 3 = 19.

Recovery Strategy:

In this case, the 2-day delay in the non-critical activity C has pushed the project completion by 2 days (from 17 to 19). To recover, the project manager can analyze the CPM network and slack:

• Activity E: Activity E still has 0 remaining slack (original slack of 2 days minus the 2-day delay in its predecessor). Any further delay in E will directly impact the project end date.
• Potential Fast-Tracking: If possible and if resources allow, the project manager could explore if any sub-tasks within Activity D or E could be performed in parallel. For example, if some design work for D can be started before the complete finalization of B, or if some initial testing for E can begin before all of C's deliverables are fully ready. The CPM network would highlight the dependencies and potential for parallelization.
• Resource Reallocation: The project manager could assess if resources can be temporarily shifted from a later, less time-sensitive non-critical activity (if one existed with significant slack) to expedite a critical sub-task within D or E. This needs careful evaluation to avoid creating new critical path issues.
• Crashing (Carefully Considered): As the delay has now impacted the project end date, the project manager might need to consider crashing an activity on the (new) critical path (A -> B -> D -> F or A -> C -> E -> F). However, crashing typically involves additional costs and should be a last resort after exploring fast-tracking and resource reallocation.

Justification:

The CPM provides the visibility needed to understand the consequences of the delay in Activity C. Initially, the slack allowed for a 2-day buffer. Once that buffer was consumed, the CPM highlighted the impact on the subsequent non-critical activity (E) and the eventual delay of the project finish date. By analyzing the CPM network, the project manager can then strategically consider options like fast-tracking or carefully reallocating resources to shorten the durations of the remaining activities, especially those that have now become part of the effective critical path due to the initial non-critical delay. The CPM allows for a data-driven approach to recovery, focusing efforts on activities that will have the most significant impact on reducing the overall project duration.

In conclusion, while CPM is primarily used for initial schedule planning and critical path identification, it is also a valuable tool for managing and recovering from schedule deviations, even in non-critical activities. By understanding slack times and the dependencies between activities, project managers can make informed decisions about resource allocation, task sequencing, and potential crashing to mitigate the impact of delays and bring the project back on track.

Sample Answer

The Critical Path Method (CPM) is a powerful project management tool that helps determine the total project duration and identify the sequence of activities that directly impact this duration – the critical path. Activities on the critical path have zero slack time, meaning any delay in these activities directly delays the project completion. However, CPM can also be strategically used to recover from schedule overruns in activities that are not on the critical path by leveraging their available slack time.

Understanding Slack Time

Before discussing recovery, it's crucial to understand slack time (also known as float). Slack time is the amount of time a non-critical path activity can be delayed without delaying the overall project completion date. Activities on the critical path have zero slack, while non-critical activities have positive slack.

How CPM Helps Recover from Non-Critical Path Overruns

When a non-critical path activity experiences a schedule overrun, the CPM helps project managers understand the following:

1. The Extent of the Delay: The CPM schedule clearly shows the original planned duration and the actual duration of the delayed activity.