3.3 Schedule Management
Key Takeaways
- The critical path is the longest sequence of activities that determines the minimum project duration — any delay on the critical path delays the project
- Float (slack) is the amount of time an activity can be delayed without affecting the project end date — critical path activities have zero float
- Schedule compression techniques include crashing (adding resources) and fast-tracking (performing activities in parallel)
- Activity dependencies include Finish-to-Start (most common), Start-to-Start, Finish-to-Finish, and Start-to-Finish (least common)
- Three-point estimating uses optimistic, most likely, and pessimistic estimates to account for uncertainty using PERT or triangular distribution
Schedule Management
Schedule management is one of the most quantitative topics on the CAPM exam. You need to understand activity sequencing, duration estimation, critical path analysis, and schedule compression techniques.
Schedule Management Processes
| Process | Process Group | Key Output |
|---|---|---|
| Plan Schedule Management | Planning | Schedule management plan |
| Define Activities | Planning | Activity list |
| Sequence Activities | Planning | Project schedule network diagram |
| Estimate Activity Durations | Planning | Duration estimates |
| Develop Schedule | Planning | Project schedule, schedule baseline |
| Control Schedule | Monitoring & Controlling | Schedule forecasts, change requests |
Activity Dependencies (Logical Relationships)
Dependencies define the relationships between activities:
| Dependency Type | Abbreviation | Description | Example |
|---|---|---|---|
| Finish-to-Start (FS) | FS | B cannot start until A finishes | Pour concrete (A) → build walls (B) |
| Start-to-Start (SS) | SS | B cannot start until A starts | Write code (A) → write documentation (B) |
| Finish-to-Finish (FF) | FF | B cannot finish until A finishes | Write code (A) → test code (B) |
| Start-to-Finish (SF) | SF | B cannot finish until A starts | New system goes live (A) → old system shuts down (B) |
Exam Tip: Finish-to-Start (FS) is the most commonly used dependency type. Start-to-Finish (SF) is the least commonly used and most confusing.
Types of Dependencies
| Type | Description | Example |
|---|---|---|
| Mandatory (Hard Logic) | Required by the nature of the work | Foundation before walls |
| Discretionary (Soft Logic) | Based on best practices or preference | Can be changed if needed |
| External | Depends on factors outside the project | Waiting for government permit |
| Internal | Between project activities | Within the team's control |
The Critical Path Method (CPM)
The critical path is the longest path through the project network diagram and determines the minimum project duration.
Key Concepts
- Critical Path Activities have zero float — any delay directly delays the project
- Non-critical activities have float (slack) — they can be delayed without affecting the project end date
- A project can have multiple critical paths (all paths tied for longest)
- The more critical paths, the higher the project risk
Calculating the Critical Path
To find the critical path:
- Identify all paths through the network
- Calculate the duration of each path
- The longest path is the critical path
Example:
| Path | Activities | Duration |
|---|---|---|
| Path 1 | A → B → D → F | 3 + 5 + 4 + 2 = 14 days |
| Path 2 | A → C → E → F | 3 + 2 + 6 + 2 = 13 days |
| Path 3 | A → B → E → F | 3 + 5 + 6 + 2 = 16 days ← Critical Path |
Critical Path = Path 3 (16 days) Float for Path 1 = 16 - 14 = 2 days Float for Path 2 = 16 - 13 = 3 days
Float (Slack)
| Type | Definition |
|---|---|
| Total Float | Amount of time an activity can be delayed without delaying the project end date |
| Free Float | Amount of time an activity can be delayed without delaying the early start of any successor |
| Project Float | Difference between the project deadline and the critical path completion date |
Duration Estimating Techniques
| Technique | Description | Best Used When |
|---|---|---|
| Analogous Estimating | Uses historical data from similar activities | Limited information available (top-down) |
| Parametric Estimating | Uses statistical relationships (e.g., cost per unit × quantity) | Quantifiable work with historical parameters |
| Three-Point Estimating | Uses optimistic (O), most likely (M), and pessimistic (P) | Accounting for uncertainty |
| Bottom-Up Estimating | Estimates individual work packages and rolls up | Detailed information available (most accurate) |
Three-Point Estimates
PERT (Beta Distribution): Expected Duration = (O + 4M + P) / 6
Triangular Distribution: Expected Duration = (O + M + P) / 3
Standard Deviation (PERT): σ = (P - O) / 6
Schedule Compression Techniques
When the schedule needs to be shortened:
| Technique | How It Works | Trade-off |
|---|---|---|
| Crashing | Add resources to critical path activities | Increases cost |
| Fast-Tracking | Perform sequential activities in parallel | Increases risk |
Exam Tip: Crashing always increases cost. Fast-tracking always increases risk. Neither technique guarantees schedule improvement, and both should target critical path activities first.
A project has three paths: Path A = 18 days, Path B = 22 days, Path C = 20 days. What is the critical path and the float for Path A?
Using PERT, what is the expected duration if the Optimistic estimate is 4 days, Most Likely is 8 days, and Pessimistic is 18 days?
Which schedule compression technique increases project RISK?
Which dependency type is the MOST commonly used in project scheduling?