PMP Exam Flashcards: Schedule Management, Critical Path, Dependencies, Estimation

The critical path method identifies the longest sequence of dependent activities that determines the minimum project duration. Any delay on a critical path activity directly delays the project completion date because these activities have zero float or slack. Non-critical activities have float, meaning they can be delayed without affecting the project end date. To find the critical path, perform a forward pass calculating early start and early finish dates, then a backward pass calculating late start and late finish dates. The difference between early and late dates is the float.

Total float is the amount of time an activity can be delayed without delaying the project end date. Free float is the amount of time an activity can be delayed without delaying the early start of any successor activity. An activity can have total float but zero free float if delaying it would delay a successor even though it would not delay the project. Critical path activities have zero total float by definition. Free float is always less than or equal to total float. The PMP exam tests both concepts and expects candidates to distinguish between them in scheduling scenarios.

The four dependency types are finish-to-start, start-to-start, finish-to-finish, and start-to-finish. Finish-to-start is the most common: the successor cannot start until the predecessor finishes, such as pouring concrete after building forms. Start-to-start means both activities start at the same time, such as writing code and writing unit tests simultaneously. Finish-to-finish means both activities must finish together, such as editing and proofreading ending at the same time.

A lead is an acceleration of the successor activity, allowing it to start before the predecessor is fully complete. For example, a finish-to-start relationship with a ten-day lead means the successor can start ten days before the predecessor finishes. A lag is a mandatory waiting time between activities. For example, a finish-to-start relationship with a five-day lag means the successor must wait five days after the predecessor finishes before it can start, such as waiting for concrete to cure before building on it. Leads compress the schedule while lags extend it.

The Program Evaluation and Review Technique, or PERT, uses three estimates to calculate a weighted average duration for an activity: optimistic, most likely, and pessimistic. The formula is optimistic plus four times the most likely plus pessimistic, all divided by six. For example, if optimistic is four days, most likely is six days, and pessimistic is fourteen days, the PERT estimate is four plus twenty-four plus fourteen divided by six, equaling seven days. PERT accounts for uncertainty better than single-point estimates.

Crashing adds resources to critical path activities to reduce their duration, such as adding overtime, hiring additional workers, or using more expensive equipment. It increases cost but compresses the schedule. Fast tracking performs critical path activities in parallel that were originally planned sequentially, such as starting construction before design is fully complete. Fast tracking does not necessarily increase cost but increases risk because parallel activities may need rework if earlier work changes. Both techniques compress the schedule but through different mechanisms.

Resource leveling adjusts the project schedule to resolve resource over-allocation by delaying activities until resources are available. When the same person or equipment is assigned to multiple activities at the same time, resource leveling shifts one activity to a time when the resource is free. This often extends the project duration because activities that could run in parallel must now run sequentially. Resource leveling may change the critical path. It is necessary when resources are limited and cannot be increased.

A Gantt chart is a horizontal bar chart that visually displays the project schedule, with activities listed vertically and time displayed horizontally. Each activity is shown as a bar spanning from its start to finish date. Gantt charts show activity durations, start and finish dates, overlapping activities, dependencies between activities shown as arrows, milestones shown as diamonds, the critical path often highlighted in a different color, and progress against the baseline. ---