A compliance percentage can hide how measured out-of-limit events differ in duration. Bands organize a report; they do not classify product impact or cause by themselves.
Define band boundaries
Choose useful ranges for operational comparison and state each lower and upper boundary. These are not product tolerances or release limits.
State measurement resolution
Duration estimates depend on logging interval. With hypothetical ten-minute records, an event near a boundary may have uncertain start and end; note it.
What the band table shows
- Short measured events: compare door, loading and stop times.
- Longer measured events: review route and run records; do not infer equipment cause alone.
- Events with gaps: mark as uncertain duration and keep them out of duration bands.
Keep bands stable across periods
If definitions change, recalculate earlier months using the same rule or mark the break clearly. Otherwise, a table change can look like improvement.
Move from band to review
Choose sample runs from each group and compare timestamps with route, loading and stop records. Do not present co-occurrence as proof of cause.
Quality assessment stays separate. Bands are only a data summary. Product assessment follows product requirements, validated route conditions and the authorized quality process.
Method note. State band boundaries, logging interval, gap rule and timestamp used. Time zone, device clock and download time can differ; keep them distinct.
