{
  "schema": "vedokrok.public-item.v1",
  "release_id": "MHC-RPUB-20260920-75ad787a",
  "url": "/knowledge/separate-the-forecast-from-the-commitment",
  "id": "MHC-D-RESEARCH-0627",
  "version": "0.1.0",
  "title": "Separate the forecast from the commitment",
  "summary": "A forecast describes uncertainty; a commitment adds a decision and consequence.",
  "kind": "principle",
  "body": "Label which statement you are making. A forecast says what the evidence suggests. A commitment says what the organization chooses to stand behind, possibly with scope, priority or reserve changes. If the commitment is tighter than the forecast, name the intervention that makes it plausible.",
  "limits": [
    "A label does not excuse chronic missed commitments; committed dates still need feasibility and accountability."
  ],
  "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 probabilistic estimate is repeated as a promise, or a management date is presented as the statistically expected date."
  ],
  "avoid_when": [
    "A label does not excuse chronic missed commitments; committed dates still need feasibility and accountability."
  ],
  "example": "'Most likely 8–10 days' can coexist with 'we commit to the 15th by cutting optional scope and reserving reviewer capacity.'",
  "check": "Stakeholders can tell whether a date came from evidence, a management choice or both.",
  "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": [],
  "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"
    }
  ]
}