開発作業にどれくらい時間がかかるかを見積もることは、よくある、難しく、重要なスキルです。見積もりは悪名高く難しい(開発者は過小評価しがち)ですが、それを改善しうまく伝えることは、計画と信頼にとって重要です。
なぜ見積もりは難しいのか
Development estimation is notoriously inaccurate:
→ UNKNOWNS → unexpected complexity, bugs, dependencies, edge cases emerge
→ OPTIMISM BIAS → developers tend to UNDERESTIMATE (imagine the happy path, forget
testing, integration, reviews, meetings, the unexpected)
→ complexity is hard to assess upfront; requirements change
→ estimates are predictions under uncertainty, not promises.
見積もりを改善する
✓ BREAK DOWN work → estimate smaller pieces (more accurate than one big guess); sum them
✓ Account for EVERYTHING → not just coding: testing, code review, integration, debugging,
meetings, unforeseen issues
✓ Use PAST EXPERIENCE → how long did similar work actually take? (reference real data)
✓ Add BUFFER for uncertainty → things take longer than the happy-path estimate
✓ Consider ranges or confidence ("3-5 days" vs a false-precise "4 days")
✓ Re-estimate as you learn more (estimates improve with information)
