7 min read • Guide 683 of 877
Improving Estimation Accuracy
Accurate estimation is crucial for planning, stakeholder communication, and team health. GitScrum helps track estimation accuracy over time, providing data to calibrate your team's estimates and improve predictability.
Understanding Estimation
Why Estimates Fail
COMMON ESTIMATION PITFALLS:
┌─────────────────────────────────────────────────────────────┐
│ │
│ OPTIMISM BIAS: │
│ "This should only take a day" │
│ → Ignores edge cases, testing, review │
│ Fix: Multiply by 1.5-2x, include all activities │
│ │
│ ANCHORING: │
│ "Last similar thing took 2 days" │
│ → Every task has unique complexity │
│ Fix: List specific differences explicitly │
│ │
│ HIDDEN COMPLEXITY: │
│ "It's just a simple change" │
│ → Integrations, edge cases, testing │
│ Fix: Spike unknown areas first │
│ │
│ REQUIREMENT GAPS: │
│ "I'll figure it out as I go" │
│ → Scope grows during development │
│ Fix: Clarify before estimating │
│ │
│ HERO SYNDROME: │
│ "I can do it faster than usual" │
│ → Sustainable pace gets ignored │
│ Fix: Estimate for average developer │
│ │
│ EXTERNAL DEPENDENCIES: │
│ "Assuming the API is ready" │
│ → Dependencies often aren't ready │
│ Fix: Include dependency risk in estimate │
└─────────────────────────────────────────────────────────────┘
Estimation Accuracy Metrics
TRACKING ESTIMATION ACCURACY:
┌─────────────────────────────────────────────────────────────┐
│ │
│ ESTIMATION ACCURACY FORMULA: │
│ │
│ Accuracy = 1 - |Estimated - Actual| / Actual │
│ │
│ EXAMPLE: │
│ Estimated: 5 points | Actual: 7 points │
│ Accuracy = 1 - |5-7|/7 = 1 - 2/7 = 71% │
│ │
│ TEAM ESTIMATION ACCURACY (Last 6 Sprints): │
│ │
│ Sprint │ Estimated │ Actual │ Accuracy │
│─────────┼───────────┼────────┼─────────────────────────────│
│ 19 │ 45 pts │ 52 pts │ 87% │
│ 20 │ 48 pts │ 46 pts │ 96% │
│ 21 │ 50 pts │ 61 pts │ 82% │
│ 22 │ 45 pts │ 48 pts │ 94% │
│ 23 │ 47 pts │ 50 pts │ 94% │
│ 24 │ 46 pts │ 49 pts │ 94% │
│ │
│ Average: 91% | Trend: Improving ↑ │
│ │
│ INSIGHT: Sprint 21 had scope creep (investigate) │
└─────────────────────────────────────────────────────────────┘
Estimation Techniques
Relative Estimation
STORY POINT ESTIMATION:
┌─────────────────────────────────────────────────────────────┐
│ │
│ REFERENCE STORIES: │
│ │
│ 1 PT: Add new field to existing form │
│ Simple, well-understood, minimal risk │
│ │
│ 2 PT: Implement basic CRUD for new entity │
│ Known patterns, some integration │
│ │
│ 3 PT: Add new feature with multiple components │
│ Moderate complexity, clear requirements │
│ │
│ 5 PT: Integrate with external API │
│ Unknown factors, needs research/testing │
│ │
│ 8 PT: Major feature with cross-cutting concerns │
│ High complexity, should consider splitting │
│ │
│ 13 PT: Too large - must be split │
│ Indicates insufficient understanding │
│ │
│ ESTIMATION PROCESS: │
│ 1. Read user story │
│ 2. Ask clarifying questions │
│ 3. Compare to reference stories │
│ 4. Team votes simultaneously (Planning Poker) │
│ 5. Discuss outliers │
│ 6. Converge on estimate │
└─────────────────────────────────────────────────────────────┘
Three-Point Estimation
THREE-POINT ESTIMATION:
┌─────────────────────────────────────────────────────────────┐
│ │
│ FOR EACH TASK, ESTIMATE: │
│ │
│ OPTIMISTIC (O): Best case, everything goes smoothly │
│ MOST LIKELY (M): Realistic scenario │
│ PESSIMISTIC (P): Worst case, obstacles encountered │
│ │
│ FORMULA (PERT): │
│ Expected = (O + 4M + P) / 6 │
│ │
│ EXAMPLE - "Implement user search": │
│ │
│ Optimistic: 2 days (simple, clear requirements) │
│ Most Likely: 4 days (some edge cases, testing) │
│ Pessimistic: 8 days (complex queries, performance) │
│ │
│ Expected = (2 + 4×4 + 8) / 6 = 4.3 days │
│ │
│ STANDARD DEVIATION: │
│ σ = (P - O) / 6 = (8 - 2) / 6 = 1 day │
│ │
│ 68% confidence: 3.3 - 5.3 days │
│ 95% confidence: 2.3 - 6.3 days │
│ │
│ USE WHEN: Communicating ranges to stakeholders │
└─────────────────────────────────────────────────────────────┘
Calibration Practices
Using Historical Data
REFERENCE-CLASS FORECASTING:
┌─────────────────────────────────────────────────────────────┐
│ │
│ STEP 1: Identify similar past work │
│ │
│ New task: "Add payment method management" │
│ Similar tasks from history: │
│ • "Add address management" - 5 pts, took 6 pts │
│ • "Add subscription management" - 8 pts, took 11 pts │
│ • "Add notification preferences" - 3 pts, took 4 pts │
│ │
│ STEP 2: Calculate adjustment factor │
│ │
│ Historical accuracy: Actual/Estimated = 1.3x average │
│ │
│ STEP 3: Adjust estimate │
│ │
│ Initial estimate: 5 points │
│ Adjusted: 5 × 1.3 = 6.5 points → 8 points (round up) │
│ │
│ STEP 4: Track and refine │
│ │
│ After completion: Compare adjusted estimate to actual │
│ Update adjustment factor for future estimates │
│ │
│ KEY: Use YOUR team's historical data, not industry │
│ averages. Every team's adjustment factor is different. │
└─────────────────────────────────────────────────────────────┘
Estimation Reviews
ESTIMATION RETROSPECTIVE:
┌─────────────────────────────────────────────────────────────┐
│ │
│ QUARTERLY ESTIMATION REVIEW (30 min) │
│ │
│ 1. ACCURACY METRICS: │
│ • Overall estimation accuracy │
│ • By story size (1pt, 2pt, 3pt, etc.) │
│ • By work type (feature, bug, tech debt) │
│ │
│ 2. OUTLIER ANALYSIS: │
│ • Which estimates were way off? │
│ • What caused the variance? │
│ • Could we have predicted the variance? │
│ │
│ 3. PATTERN RECOGNITION: │
│ • Do we consistently under/overestimate? │
│ • Which types of work have most variance? │
│ • Are certain estimators more accurate? │
│ │
│ 4. CALIBRATION UPDATES: │
│ • Update reference stories if needed │
│ • Adjust estimation techniques │
│ • Update team's adjustment factor │
│ │
│ OUTPUT: │
│ • Updated estimation guidelines │
│ • Identified patterns to watch │
│ • Calibrated reference points │
└─────────────────────────────────────────────────────────────┘
Communication
Communicating Estimates
ESTIMATE COMMUNICATION:
┌─────────────────────────────────────────────────────────────┐
│ │
│ TO STAKEHOLDERS: │
│ │
│ ✓ GOOD: "Based on our historical data, this feature │
│ will take 2-3 sprints. Our team completes │
│ 90% of work within estimated ranges." │
│ │
│ ✗ BAD: "It will take exactly 4 weeks." │
│ (False precision, sets wrong expectations) │
│ │
│ ───────────────────────────────────────────────── │
│ │
│ CONFIDENCE LEVELS: │
│ │
│ HIGH CONFIDENCE (±20%): │
│ "Similar to work we've done before" │
│ "Requirements are clear" │
│ "No external dependencies" │
│ │
│ MEDIUM CONFIDENCE (±40%): │
│ "Some unknowns to resolve" │
│ "New technology but understood problem" │
│ "External dependencies with committed dates" │
│ │
│ LOW CONFIDENCE (±100%): │
│ "Need spike/research first" │
│ "Novel problem and technology" │
│ "Many external dependencies" │
└─────────────────────────────────────────────────────────────┘