3.3 Schedule Management

The Six Schedule Processes

Schedule management is the most calculation-heavy area of the CAPM exam. Master the process flow, then the math.

Logical Relationships (Dependencies)

FS is by far the most common; SF is rarest. Dependencies are also classified as mandatory (hard logic, required by the work), discretionary (soft logic, preferred practice), external (e.g., a permit), or internal (within team control). Leads pull a successor earlier (FS minus 2 days); lags push it later (FS plus 2 days).

Critical Path Method

The critical path is the longest path through the network; it sets the project's minimum duration. Its activities have zero total float, so any slip delays the whole project. A project may have multiple critical paths, which raises risk.

Worked example:

Critical path = 16 days. Total float of Path 1 = 16 − 14 = 2 days; Path 2 = 16 − 13 = 3 days.

Float (Slack)

Total float = Late Start − Early Start = Late Finish − Early Finish. A forward pass computes early dates; a backward pass computes late dates.

Duration Estimating

Three-point math (memorize):

• PERT (beta): Expected = (O + 4M + P) / 6
• Triangular: Expected = (O + M + P) / 3
• PERT standard deviation: σ = (P − O) / 6

Example: O = 4, M = 8, P = 18 → PERT = (4 + 32 + 18) / 6 = 9 days; σ = (18 − 4) / 6 ≈ 2.3 days.

Compression and Resource Optimization

Exam tip: Both compression techniques target the critical path. Crash when budget allows risk-aversion; fast-track when schedule pressure outweighs rework risk.

Forward Pass, Backward Pass, and Reading Floats

The network calculation has two halves. The forward pass moves left to right, adding durations to compute each activity's early start (ES) and early finish (EF); it tells you the soonest each task can happen. The backward pass moves right to left from the project finish, subtracting durations to compute late start (LS) and late finish (LF); it tells you the latest each task can happen without delaying the project. Total float for any activity is then LS − ES (equivalently LF − EF). Critical-path activities, by definition, have ES = LS and EF = LF, so their float is zero.

A frequent exam wrinkle: an imposed deadline earlier than the calculated finish creates negative float, signaling the schedule is already infeasible and must be compressed.

Estimating Pitfalls and Reserves

Watch the difference between effort and duration: 40 hours of effort for one person is roughly a one-week duration, but two people might compress it — subject to whether the work can be parallelized. Padding individual estimates is discouraged; instead, identified schedule risk is handled with contingency reserve (buffer for known risks, inside the baseline) and unknown risk with management reserve (outside the baseline).

Three-point estimating gives you a defensible range rather than a single optimistic guess, and the PERT standard deviation lets you express confidence — roughly 68% of outcomes fall within one σ of the expected value under a normal approximation.

Schedule Network Diagram Conventions

Most modern scheduling uses the precedence diagramming method (PDM), also called activity-on-node, where boxes are activities and arrows are dependencies. This is what supports the four relationship types (FS, SS, FF, SF) and leads and lags. An older approach, activity-on-arrow, supports only finish-to-start. Milestones are zero-duration markers used to flag key checkpoints such as a phase gate or a customer review; because they consume no time, they never appear on the critical path as duration but can still anchor dependencies.

Control Schedule in Practice

During execution, Control Schedule compares actual progress to the schedule baseline, often using SPI from Earned Value, and produces schedule forecasts and change requests. If the project falls behind, the manager evaluates crashing versus fast-tracking, models the trade-offs, and routes any baseline change through integrated change control — the schedule baseline is never edited informally. Remember that resource leveling can lengthen the critical path because it respects resource limits, whereas resource smoothing stays within available float and therefore cannot.