The longest sequence of dependent activities from start to finish that dictates the shortest possible time to complete the entire project.
Simple Real-World Example:
Imagine making breakfast. Brewing coffee takes 5 minutes. Toasting bread takes 2 minutes, and frying an egg takes 4 minutes after toasting. Toast → Egg takes $2 + 4 = 6\text{ minutes}$, so it is the Critical Path. If the egg is delayed by 1 minute, the entire breakfast is delayed by 1 minute!
Any delay on a critical activity directly pushes back the final handover date.
Calculated during the Forward Pass. ES is the earliest possible date a task can start as soon as all predecessors finish. EF is the earliest it can be completed.
Simple Real-World Example:
If building the server room foundation finishes on Day 10, the earliest you can start laying cables (ES) is Day 11. If cable laying takes 5 days, its Early Finish (EF) is Day 15.
Calculated during the Backward Pass. LF is the latest time an activity can finish, and LS is the latest it can start, without delaying the contract completion deadline.
Simple Real-World Example:
If your project must finish by Day 100 and final inspection takes 4 days, the Late Finish (LF) for cleaning is Day 96, and Late Start (LS) is Day 92. Starting after Day 92 will delay final delivery.
Total Float is the leeway a task has before delaying the project end date. Free Float is the leeway a task has before delaying the very next task.
Simple Real-World Example:
Ordering office chairs can start on Day 5 (ES) or as late as Day 25 (LS) without delaying the office opening. It has 20 days of Total Float (Safe buffer!).
The budgeted monetary value of the physical work that has actually been finished up to the status date.
Simple Real-World Example:
You have a contract to install 100 RTU cabinets for a total budget of $100,000 ($1,000 each). Today, your team has physically completed 40 cabinets. Your Earned Value is $40\% \times \$100,000 = \mathbf{\$40,000}$.
The authorized budget assigned to scheduled work that was supposed to be completed by today according to the original baseline plan.
Simple Real-World Example:
In the same 100-cabinet project, your original schedule called for completing 50 cabinets by the end of Month 3. Your Planned Value is $50\% \times \$100,000 = \mathbf{\$50,000}$.
The total financial cost actually incurred and paid to accomplish the work performed up to the status date.
Simple Real-World Example:
To finish those 40 cabinets, you paid technicians and purchased parts totaling $38,000. Your Actual Cost is $\mathbf{\$38,000}$.
Measures timeline delivery efficiency and execution velocity compared to the plan.
Simple Real-World Example:
$EV = \$40,000$ and $PV = \$50,000 \implies SPI = \frac{40,000}{50,000} = \mathbf{0.80}$. You are progressing at 80% of your planned speed (20% behind schedule!).
Rule: SPI > 1.0 (Ahead of Plan) • SPI = 1.0 (On Schedule) • SPI < 1.0 (Delayed)
Measures the cost efficiency of budgeted resources expended on the project.
Simple Real-World Example:
$EV = \$40,000$ and $AC = \$38,000 \implies CPI = \frac{40,000}{38,000} = \mathbf{1.05}$. For every $1.00 spent, you earned $1.05 of work (Under budget / favorable!).
Rule: CPI > 1.0 (Under Budget) • CPI = 1.0 (On Budget) • CPI < 1.0 (Over Budget)
The cost efficiency the team must maintain for all remaining work to finish within the original budget.
Simple Real-World Example:
If $TCPI = 0.95$, remaining tasks can be done with relaxed efficiency. If $TCPI = 1.25$, the remaining team must perform 25% more efficiently than budget to avoid cost overruns.
Accounts for uncertainty by calculating a weighted average of three scenarios: Optimistic (O), Most Likely (M), and Pessimistic (P).
Simple Real-World Example:
Underground optical fiber trenching: Best case $O = 10\text{d}$, Normal case $M = 15\text{d}$, Worst case (heavy rain) $P = 32\text{d}$.
Expected Duration $T_e = \frac{10 + 4(15) + 32}{6} = \mathbf{17.0\text{ Days}}$ ($\sigma = \pm 3.7\text{d}$).
Crashing adds extra resources (overtime, double shifts) to critical tasks at higher cost. Fast-Tracking runs sequential tasks in parallel to save time with higher risk.
Simple Real-World Example:
Crashing: Hiring a second shift of test engineers to finish RTU point-to-point testing in 100 days instead of 120 days (Costs an extra $24,000).
Fast-Tracking: Starting SCADA display graphic building before server room hardware mounting is 100% completed.
The logical links that govern task start and finish triggers.
Simple Real-World Example:
• FS (Finish-to-Start): Must finish hardware installation before starting RTU point-to-point test.
• SS (Start-to-Start): Can begin drafting test reports as soon as testing commences.
• FF (Finish-to-Finish): Final documentation cannot finish until site acceptance testing finishes.
Balancing monthly workload demand from active tasks against team member availability to prevent burnout and project bottlenecks.
Simple Real-World Example:
One engineer can work 22 days per month. If active tasks in July require 32 engineer-days, that engineer is over-allocated by 10 days (145%) and needs an assistant or task leveling.
A hierarchical decomposition of the total project scope into manageable deliverables and measurable work packages.
Simple Real-World Example:
Level 1 (Phase): 8.0 Installation of SCADA/ADMS
Level 2 (Deliverable): 8.2 Hardware & Software Installation
Level 3 (Work Package): 8.2.1 Cable Laying & Termination.