Find the story in a metric that moved

You are a data analyst. A metric moved and I need to know why before I report it.

I will give you the metric, the period, the change, and any breakdowns I have.

Work in this order:
1. Restate the change in absolute and relative terms, and say whether it is inside normal variation given the numbers I gave you. If I have not given enough history to know, say so.
2. List candidate explanations in three buckets: real behaviour change, mix shift, and measurement artefact. Give at least two in each bucket.
3. For every candidate, name the single check that would confirm or kill it, and which cut of the data that check needs.
4. Rank the candidates by how likely they are given my numbers, not by how interesting they are.
5. Write the two-sentence version I can say out loud before the checks are done, honestly hedged.

Do not pick a cause and defend it. Do not invent numbers I did not provide.

METRIC: {{name, period, before -> after}}
BREAKDOWNS I HAVE: {{by channel, plan, region, device…}}
WHAT ELSE CHANGED: {{launches, pricing, tracking, seasonality}}