{
  "schema": "vedokrok.public-item.v1",
  "release_id": "MHC-RPUB-20260920-75ad787a",
  "url": "/knowledge/pin-the-scope-snapshot-to-every-material-forecast",
  "id": "MHC-D-RESEARCH-0629",
  "version": "0.1.0",
  "title": "Pin the scope snapshot to every material forecast",
  "summary": "A forecast can be wrong; it can also be about a different job.",
  "kind": "protocol",
  "body": "Store the estimate with its scope version or a short snapshot of included deliverables, assumptions and dependencies. When scope changes materially, create a new forecast and preserve the old one for learning rather than silently editing history.",
  "limits": [
    "Do not freeze harmless wording changes into formal re-estimation; use a materiality threshold appropriate to the work."
  ],
  "topics": [
    "union-project-estimation-and-delivery-realism"
  ],
  "intents": [],
  "source_ids": [
    "RS-F874002E4A58CC3B",
    "RS-B3FC6B5B65061AB3"
  ],
  "evidence": [
    {
      "claim": "The 2026 Green Book recommends explicitly accounting for optimism bias in cost, benefit and duration estimates and using historical forecast errors from similar proposals where available.",
      "source_id": "RS-F874002E4A58CC3B",
      "role": "supports",
      "note": "The guidance is for UK public appraisal; the transferable principle is empirical correction, not a universal percentage uplift.",
      "locator": "Optimism bias"
    },
    {
      "claim": "IPA guidance notes that uncertainty and estimate range depend on the maturity and variability of input data, so estimates should evolve as design and evidence mature.",
      "source_id": "RS-B3FC6B5B65061AB3",
      "role": "supports",
      "note": "A later estimate can still be wrong; maturity narrows uncertainty only when real information has improved.",
      "locator": "Estimate maturity and range"
    }
  ],
  "use_when": [
    "A forecast is later judged against a project that changed shape."
  ],
  "avoid_when": [
    "Do not freeze harmless wording changes into formal re-estimation; use a materiality threshold appropriate to the work."
  ],
  "example": "The original estimate covered 1,000 records; after the scope grows to 1,800, the revised estimate is a new forecast rather than a rewrite of the original.",
  "check": "Forecast error can be separated from scope change.",
  "steps": [
    "Forecast date recorded.",
    "Scope/version recorded.",
    "Key assumptions recorded.",
    "Material change creates a new forecast.",
    "Old forecast preserved for calibration."
  ],
  "sources": [
    {
      "id": "RS-F874002E4A58CC3B",
      "title": "The Green Book (2026)",
      "url": "https://www.gov.uk/government/publications/the-green-book-appraisal-and-evaluation-in-central-government/the-green-book-2026"
    },
    {
      "id": "RS-B3FC6B5B65061AB3",
      "title": "Cost Estimating Guidance",
      "url": "https://www.gov.uk/government/publications/cost-estimating-guidance/cost-estimating-guidance"
    }
  ],
  "relations": [
    {
      "from": "MHC-D-RESEARCH-0629",
      "to": "MHC-D-RESEARCH-0630",
      "type": "use_before",
      "url": "/knowledge/re-estimate-when-evidence-changes-not-when-anxiety-spikes"
    }
  ],
  "collections": [
    {
      "id": "RC-3C67E080415E2677",
      "title": "Estimate the delivery system, not only the hands-on work",
      "url": "/collections/estimate-the-delivery-system-not-only-the-hands-on-work"
    }
  ]
}