Key Takeaways
- Cost estimating techniques include analogous (least accurate), parametric (uses statistical relationships), bottom-up (most accurate), and three-point (PERT) estimating
- The cost baseline is the approved time-phased budget used to measure and monitor cost performance, excluding management reserves
- Contingency reserves address identified risks (known unknowns) and are part of the cost baseline, while management reserves address unidentified risks (unknown unknowns)
- Estimate accuracy improves through project phases: ROM (-25% to +75%), Budget (-10% to +25%), and Definitive (-5% to +10%)
- Earned Value Management (EVM) uses Cost Performance Index (CPI = EV/AC) and Schedule Performance Index (SPI = EV/PV) to measure project performance
Planning & Managing Budget
Cost management ensures the project is completed within the approved budget. It involves estimating costs, determining the budget, and controlling expenditures throughout the project.
Cost Management Processes
| Process | Purpose | Key Output |
|---|---|---|
| Plan Cost Management | Establish policies and procedures for cost management | Cost Management Plan |
| Estimate Costs | Approximate monetary resources needed | Cost Estimates |
| Determine Budget | Aggregate estimates to establish cost baseline | Cost Baseline |
| Control Costs | Monitor status and manage cost changes | Work Performance Information |
Cost Estimating Techniques
Comparison of Techniques
| Technique | Accuracy | Time/Cost | Best Used When |
|---|---|---|---|
| Analogous | -25% to +75% | Lowest | Early phases, limited information |
| Parametric | -10% to +25% | Moderate | Historical data available |
| Bottom-Up | -5% to +10% | Highest | Detailed WBS available |
| Three-Point | Varies | Moderate | Uncertainty exists |
Analogous Estimating (Top-Down)
Uses costs from previous similar projects as the basis for estimates:
Example: "The last website project cost $50,000, so this similar one should cost about $50,000."
| Advantage | Disadvantage |
|---|---|
| Quick and inexpensive | Less accurate |
| Useful with limited information | Depends on similarity |
| Good for high-level budgeting | May not account for differences |
Parametric Estimating
Uses statistical relationships between historical data and other variables:
Example: Cost per line of code x estimated lines of code
| Cost Parameter | Unit Rate | Quantity | Estimate |
|---|---|---|---|
| Software coding | $50/line | 10,000 lines | $500,000 |
| Testing | $20/test case | 500 cases | $10,000 |
| Documentation | $100/page | 200 pages | $20,000 |
| Total | $530,000 |
Bottom-Up Estimating
Estimates individual work packages and aggregates them:
Project Total: $530,000
├── Phase 1: $80,000
│ ├── WP 1.1: $30,000
│ └── WP 1.2: $50,000
├── Phase 2: $250,000
│ ├── WP 2.1: $100,000
│ ├── WP 2.2: $100,000
│ └── WP 2.3: $50,000
└── Phase 3: $200,000
├── WP 3.1: $150,000
└── WP 3.2: $50,000
- Most accurate estimating technique
- Most time-consuming and expensive
- Requires detailed WBS
Three-Point Estimating
Uses optimistic, most likely, and pessimistic estimates:
Beta/PERT Formula: E = (O + 4M + P) / 6
Triangular Formula: E = (O + M + P) / 3
Example:
- Optimistic: $80,000
- Most Likely: $100,000
- Pessimistic: $150,000
PERT Estimate = ($80,000 + 4($100,000) + $150,000) / 6 = $103,333
Estimate Accuracy Levels
| Level | Accuracy Range | Project Phase | Purpose |
|---|---|---|---|
| Rough Order of Magnitude (ROM) | -25% to +75% | Initiation | Feasibility, go/no-go decisions |
| Budget Estimate | -10% to +25% | Planning | Budget authorization |
| Definitive Estimate | -5% to +10% | Detailed Planning | Baseline, contracts |
Progressive Elaboration of Estimates
Estimates become more accurate as the project progresses:
- Initiation: ROM estimate based on analogous data
- Early Planning: Budget estimate using parametric methods
- Detailed Planning: Definitive estimate using bottom-up approach
Cost Baseline Development
The Cost Baseline is the approved, time-phased budget used to measure and monitor project cost performance.
From Estimates to Baseline
| Component | Description | Included in Baseline? |
|---|---|---|
| Activity Cost Estimates | Cost of individual activities | Yes |
| Contingency Reserves | For identified risks (known unknowns) | Yes |
| Cost Baseline | Time-phased spending plan | Yes |
| Management Reserves | For unidentified risks (unknown unknowns) | No |
| Project Budget | Cost Baseline + Management Reserves | Total funding |
Visual Representation
Project Budget
↓
┌─────────────────────────────────────┐
│ Management Reserves │ ← Unknown unknowns
├─────────────────────────────────────┤
│ Cost Baseline │ ← Performance baseline
│ ┌─────────────────────────────┐ │
│ │ Contingency Reserves │ │ ← Known unknowns
│ ├─────────────────────────────┤ │
│ │ Activity Cost Estimates │ │ ← Work package costs
│ └─────────────────────────────┘ │
└─────────────────────────────────────┘
Contingency and Management Reserves
Contingency Reserves
- Address identified risks (known unknowns)
- Part of the cost baseline
- PM has authority to use
- Calculated through risk analysis
Management Reserves
- Address unidentified risks (unknown unknowns)
- NOT part of the cost baseline
- Requires sponsor approval to use
- Typically a percentage of project budget
Reserve Calculation Example
| Component | Amount | Calculation |
|---|---|---|
| Base Estimate | $400,000 | Sum of activity estimates |
| Contingency Reserve | $40,000 | 10% for identified risks |
| Cost Baseline | $440,000 | Base + Contingency |
| Management Reserve | $44,000 | 10% of baseline |
| Project Budget | $484,000 | Baseline + Management Reserve |
Funding Requirements
The funding limit reconciliation ensures that expenditures are reconciled with funding limits:
Funding Patterns
| Pattern | Description | Example |
|---|---|---|
| Front-loaded | More funding early | Capital purchases upfront |
| Back-loaded | More funding later | Labor-intensive completion |
| Linear | Even spending over time | Steady-state operations |
| S-Curve | Gradual start, peak, gradual end | Typical project pattern |
Cash Flow Planning
- Identify when funds are needed
- Align with organizational funding cycles
- Account for payment terms with vendors
- Consider revenue timing if applicable
Earned Value Management (EVM) Basics
Earned Value Management integrates scope, schedule, and cost to assess project performance.
Key EVM Metrics
| Metric | Formula | Meaning |
|---|---|---|
| Planned Value (PV) | Budgeted cost of work scheduled | What should have been done |
| Earned Value (EV) | Budgeted cost of work performed | What has been accomplished |
| Actual Cost (AC) | Actual cost of work performed | What was actually spent |
Performance Indices
| Index | Formula | Interpretation |
|---|---|---|
| Cost Performance Index (CPI) | EV / AC | > 1.0 = Under budget, < 1.0 = Over budget |
| Schedule Performance Index (SPI) | EV / PV | > 1.0 = Ahead of schedule, < 1.0 = Behind schedule |
Variance Analysis
| Variance | Formula | Interpretation |
|---|---|---|
| Cost Variance (CV) | EV - AC | Positive = Under budget |
| Schedule Variance (SV) | EV - PV | Positive = Ahead of schedule |
Example
| Metric | Value |
|---|---|
| PV (Planned) | $100,000 |
| EV (Earned) | $80,000 |
| AC (Actual) | $90,000 |
| CPI | 0.89 (over budget by 11%) |
| SPI | 0.80 (behind schedule by 20%) |
| CV | -$10,000 (over budget) |
| SV | -$20,000 (behind schedule) |
Key Takeaways
- Analogous is fastest but least accurate; Bottom-up is most accurate but slowest
- Parametric uses statistical relationships with historical data
- Three-point accounts for uncertainty using optimistic, most likely, and pessimistic estimates
- Contingency reserves are for identified risks and are in the cost baseline
- Management reserves are for unidentified risks and are NOT in the cost baseline
- EVM uses PV, EV, and AC to measure cost and schedule performance
Which cost estimating technique is MOST accurate and uses detailed estimates of individual work packages?
A project has a budget of $500,000 including $50,000 in contingency reserves and $45,000 in management reserves. What is the cost baseline?
A project has PV = $200,000, EV = $180,000, and AC = $210,000. What is the Cost Performance Index (CPI) and what does it indicate?