Definitions drift
If response intervals, priority groups or canceled calls are defined differently across reports, the numbers may disagree even when both queries run correctly. A governed metric dictionary is part of the analytical product.
Operational clocks are imperfect
Timestamp behavior changes with dispatch workflow, device use and interface design. Outliers, missing events and impossible sequences need explicit treatment before aggregation.
Joins and workflow changes matter
Duplicate incident keys, incomplete unit records and software transitions can introduce silent bias. Dashboards should expose freshness, exclusions and quality checks so viewers know what the measure can support.