OPS.18:4.2 - Select the evidence branch
| Current question | Evidence method | First operating use |
|---|---|---|
| Has a recurring process changed from its established behavior? | A suitable statistical monitor with a qualified baseline, sampling rule and response policy. | Continue observation or investigate and contain the affected process/result. |
| Is event-based service meeting its objective? | Good/eligible event definitions, observation coverage, window, permitted loss and a response policy. | Adjust continuation or change activity under the service decision. |
| Should a particular lot or result be accepted? | Its qualified acceptance plan, defect definitions, sampling basis and relevant risks. | Accept, reject, segregate, rework or obtain the missing acceptance result. |
| Can an impaired service be restored or restarted? | Evidence of the failure, containment or repair, and the required restart conditions. | Restore service under the appropriate authority and continue any unresolved investigation. |
| What prevention does an incident or near miss need? | Reconstructed events, material explanations and sufficient support for feasible protective measures. | Select and verify prevention under :4.4, retaining the limits on the causal conclusion. |
Branches can be complementary. Select each because its answer changes the current action. A favorable result from one branch cannot supply the evidence required by another.
For recurring variation, recover whether observations are comparable, whether the baseline is appropriate and whether the selected model fits the data. Independence, changing sample size, seasonality, clustering or rare events can change the required monitor. A simple chart should yield to a qualified statistical method when its assumptions or detection performance are inadequate.
For an event-based service, define the good and eligible events from the recipient’s experience. Check omitted events, important subgroups and observation delay. A fast failure can require a timely alert before an end-of-window aggregate is available.
For acceptance, recover the lot or item, what counts as a defect, the sampling/inspection method, and the consequences of accepting unacceptable output or rejecting acceptable output. Obtain the qualified plan where it is missing. An operating practitioner can use a supplied plan without deriving its statistical design anew.