Aglet

Learn From Repeated Ratio Denominator Confusion

A denominator lesson preserves the small population where one numerator produced competing rates. Record eligibility, exclusions, zero behavior, formula, label, and decision context. Then improve the metric dictionary and report review so future ratios expose their denominator before a threshold or trend is used.

Keep the lesson for the next incident

  1. Keep the population example

    Retain numerator successes, eligible non-successes, excluded rows, repeated memberships, and zero-eligible cases with expected rates. Record filters, period, precision, visible label, and export header. Preserve the original ambiguous wording beside the agreed definition.

  2. Classify prior disputes

    Review earlier ratio questions for hidden eligibility, denominator changes, join fanout, filter scope, rounding, and zero handling. Group examples by missing contract or review signal. Use named populations and observed decisions rather than assigning an unsupported frequency.

  3. Assign metric stewardship

    Make the metric owner maintain the numerator and denominator definition, and the report owner check it after filter or join changes. Add a review trigger for eligibility-policy changes. State which population cases the fixture detects and which policy alternatives still require human agreement.

What to carry forward

The learning record is complete when it ties ratio confusion to a missing population contract, preserves a fixture with competing denominators, and names an owner and trigger. Keep intentionally different rates labeled with their eligibility rules so future readers do not reopen a settled distinction.

Technical background: Metabase documentation.

Keep the decision with the work.

Use a Work Item in Aglet to record the problem, the evidence you have, and the next decision. Add an owner and priority, then keep updates in the discussion so the next person can follow the reasoning.

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