What to remember
- Start from the user job and business objective before naming a metric.
- Separate outcome, input, quality, and guardrail metrics.
- Validate the data and locate the broken funnel step before explaining a decline.
- State experiment unit, duration, practical significance, and decision rule.
Build a metric tree from the product job
A metric tree explains how user behavior produces an outcome. It also gives you places to investigate when performance changes.
A metric can be useful without being the north star. Click-through rate may explain discovery, but it can reward curiosity without value. Revenue may matter to the business, but it can lag product quality or conceal who is being harmed.
- North-star outcome: the recurring action that best represents delivered value.
- Reach: eligible users who encounter the product.
- Activation: users who complete the first meaningful action.
- Depth or quality: whether the action actually solves the job.
- Retention: whether users return when the need recurs.
- Guardrails: safety, trust, latency, cost, fairness, or ecosystem harm.
Worked example: measuring saved job searches
Suppose a job marketplace launches saved searches that alert candidates when relevant roles appear.
Diagnose a metric drop in the right order
Use four passes: definition, shape, segmentation, explanation. Fixing before diagnosis is guesswork.
You do not need to write SQL in every PM interview. Knowing how you would define the population and compare funnel stages demonstrates analytical precision, even when an analyst would run the final query.
- Definition: did event logic, eligibility, deduplication, or the denominator change?
- Shape: when did the movement start, was it sudden or gradual, and is it statistically unusual?
- Segmentation: where is the effect concentrated by platform, version, market, cohort, source, or journey step?
- Explanation: which release, operational event, market shift, or behavior change matches that pattern?
WITH funnel AS (
SELECT user_id,
MAX(CASE WHEN event = 'alert_opened' THEN 1 ELSE 0 END) AS opened,
MAX(CASE WHEN event = 'job_viewed' THEN 1 ELSE 0 END) AS viewed,
MAX(CASE WHEN event = 'application_sent' THEN 1 ELSE 0 END) AS applied
FROM product_events
WHERE event_date >= CURRENT_DATE - INTERVAL '14 days'
GROUP BY user_id
)
SELECT AVG(opened), AVG(viewed), AVG(applied)
FROM funnel;Design an experiment with a decision rule
An experiment answer should cover hypothesis, unit, population, metrics, duration, risks, and the action you will take after the result.
Randomize at the level where treatment can spill over. A marketplace change may require geographic or seller-level randomization rather than user-level assignment. Run through relevant cycles such as weekdays and weekends, and define the minimum effect that is worth the operational cost.
- Name the causal hypothesis in one sentence.
- Choose a primary metric before seeing the result.
- Set guardrails and stopping criteria for harm.
- Inspect heterogeneous effects for major user groups.
- Explain what ship, iterate, or stop would each require.
Handle metric conflicts as product decisions
When one metric improves and another declines, translate both into user and business consequences.
Common questions
Do PMs need SQL for metrics interviews?
Many roles do not require writing production SQL, but you should be able to define events, populations, joins, time windows, and comparisons precisely. Technical PM and data-heavy roles may test SQL directly.
What is a good north-star metric?
It should represent recurring user value, be sensitive enough to guide product work, and resist easy manipulation. It should be paired with guardrails rather than expected to describe the entire business alone.
How do I answer when there is no data?
State the decision, identify the highest-risk assumption, and propose the fastest credible evidence source. This might be a prototype test, instrumented pilot, operational sample, or carefully chosen proxy.
Research sources
Primary and institutional sources lead. Supporting reports are used only for clearly qualified patterns or changes and are labelled in their notes.
A general guide gets you started. Your dossier gets specific.
Build a cited preparation brief for your company, role, seniority, and interview stage.