Final answer:
To calculate early, late, and slack times in a project network plan, a timeline should be created to determine the project duration and identify potential slacks. The longest path, known as the critical path, defines the project duration, and slack is the flexibility in an activity's completion time without affecting the overall project. Comparing estimated and actual times can reveal estimation accuracy and the impact of unforeseen events.
Step-by-step explanation:
To calculate the early, late, and slack times in a network plan, one must analyze the sequence of activities and their respective durations. The first step is to create a timeline, consisting of early start, early finish, late start, and late finish times for each activity.
The project duration is determined by the longest path through the network, which is the critical path. The slack or float is the amount of time that an activity can be delayed without delaying the project. It's identified by subtracting the early start from the late start or the early finish from the late finish of an activity.
After you have calculated these times for each activity and determined the critical path, you can draw a conclusion about the project's duration. During the execution, comparing the estimated times with the actual ones can provide insight into the accuracy of your estimations and identify any unexpected outcomes. Such outcomes may result from unforeseen events that impacted the completion times of activities during that stage.
Sometimes, activities may finish earlier or later than expected despite the planned durations, which could be due to various factors like resource availability, unforeseen obstacles, or improved efficiencies. It's crucial to analyze and understand these discrepancies for future project planning and management.