aj-geddes Estimation
Process
1. Decompose Exhaustively
Break tasks until each piece is < 8 hours and estimatable with confidence.
Task: "Add user authentication"
├─ Database schema (2h)
├─ API endpoints (16h) → decompose further
├─ Password handling (8h)
├─ JWT tokens (19h) → decompose further
├─ Middleware (14h) → decompose further
├─ Testing (23h) → decompose further
└─ Integration (22h) → decompose further
Rule: If you can't estimate confidently, decompose further.
2. Identify Unknowns
unknowns:
technical: ["Never used bcrypt", "Don't know JWT refresh pattern"]
domain: ["Password rules unspecified", "SSO needed later?"]
external: ["DBA review has 2-day SLA"]
resource: ["Frontend dev availability uncertain"]
Every unknown adds risk. Quantify it.
3. Three-Point Estimate
For each atomic task:
| Estimate | Meaning |
|---|---|
| Optimistic (O) | Everything goes perfectly |
| Realistic (R) | Normal conditions, typical hiccups |
| Pessimistic (P) | Murphy's Law applies |
"Implement password hashing"
O: 1h (copy existing pattern)
R: 3h (read docs, test, handle edge cases)
P: 8h (version issues, need alternatives)
Rule: If P > 3x R, decompose further.
4. Calculate PERT
Expected = (O + 4*R + P) / 6
Example: (1 + 4*3 + 8) / 6 = 3.5h
5. Apply Risk Buffers
| Risk Level | Multiplier | When |
|---|---|---|
| Low | 1.0-1.2x | Well-understood, clear requirements |
| Medium | 1.2-1.5x | Some unknowns, moderate complexity |
| High | 1.5-2.0x | New tech, unclear requirements |
| Critical | 2.0-3.0x | Multiple unknowns, bleeding-edge |
Risk categories:
| Category | Multiplier | Triggers |
|---|---|---|
| Technical | 1.3-2.0x | New lang/framework, complex algorithms, perf requirements |
| Domain | 1.4-2.5x | Unclear requirements, regulatory, stakeholder disagreement |
| External | 1.5-3.0x | Third-party deps, vendor timelines, cross-team |
| Resource | 1.2-2.0x | Availability uncertain, skills gap, access issues |
6. Add Integration Buffer
Integration is where 50% of bugs live. Always add 20-30%.
Subtasks total: 40h
Integration buffer (25%): 10h
Final: 50h
Anti-Patterns
| Anti-Pattern | Problem | Fix |
|---|---|---|
| "2 Hours" | "I have no idea" | Use three-point + PERT |
| Secret Padding | Destroys trust | State explicit buffer: "5h + 5h buffer" |
| Ignoring Integration | Underestimate 30-50% | Always add integration buffer |
| Forgetting Testing | "Done" != done | Include test time (often 1:1 with dev) |
| No Confidence Level | False precision | Use ranges: "45h +/- 5h" |
Communication Template
[ESTIMATE] (+/-[UNCERTAINTY]) assuming [ASSUMPTIONS]
Breakdown:
- Component 1: Xh
- Component 2: Yh
- Integration: Zh
Confidence: [High/Medium/Low] (XX%)
Assumptions:
1. [Critical assumption]
Risks:
- [Risk]: [impact] / [mitigation]
Dependencies:
- [External dependency]
Unknowns:
- [Unknown] - [how to resolve]
Validation Checklist
Before finalizing any estimate:
- Decomposed into atomic units (< 8h each)
- Every subtask has O/R/P estimates
- PERT formula applied
- All unknowns identified
- Risk buffers applied
- Integration buffer added (20-30%)
- Confidence level assigned
- Assumptions stated
- Risks identified with mitigations
- Dependencies noted
- Estimate is a range (+/- X)
When to Re-Estimate
- Requirements change -- re-decompose affected components
- Unknown resolved -- update with actual findings
- Overrun > 20% -- stop and reassess remaining work
- Dependency changes -- adjust timeline
- Team changes -- different skills = different estimates
Script
Run the interactive PERT estimation helper:
skills/estimation/scripts/estimate.sh
# or
./scripts/estimate.sh [--output filename]
References
references/decomposition-examples.md-- full worked examplesreferences/risk-analysis.md-- risk assessment frameworkreferences/communication-guide.md-- stakeholder communication patternsscripts/estimate.sh-- interactive PERT estimation script