Model discrete risk events and responses

Write each event as cause – uncertain event – effect. A condition that has already happened is usually part of the baseline or current scope, not a probabilistic event. Classify the event as a threat or opportunity, assign an owner and status, and link the evidence that supports its occurrence probability and impact ranges.

Probability governs whether the event occurs in an iteration. Cost and schedule impact distributions describe non-negative magnitudes. The engine adds threats and subtracts opportunities while preventing negative total cost or duration. Do not use a signed impact range to reverse the declared kind. Avoid using one event to cover both a known estimate omission and an uncertain future occurrence.

Inherent and residual profiles

The inherent profile is exposure before the stated response. The residual profile is a new, supportable claim after a response; it is never calculated automatically from the inherent profile. A reduced residual probability or impact requires a concrete response strategy, action, owner, due date, credible status, rationale, and evidence or explicit assumption. Missing residual values do not fall back to inherent values.

Opportunities need the same discipline as threats. Response choices may pursue, enhance, share, or accept an opportunity, but optimistic impacts must not compensate for poorly modeled threats. Close or exclude events only with a clear basis. Scenario overrides are bounded what-if assumptions and never rewrite the canonical event. For schedule impacts, identify whether the effect applies to project finish or a named activity. Continue to schedule networks and duration. ## Interpretation discipline

Keep inputs, derived results, and human decisions visibly separate. Every material number needs linked evidence or an explicit assumption flag and basis. Unknown is not zero. A percentile is conditional on this model, scenario, seed, engine version, and source version; it is neither a guarantee nor an approval. Any material model edit makes an earlier result stale.