This interview question evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer for Design Metrics to Track and Analyze Spam Impact states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
##### Scenario
Product team wants metrics and experiment design to reduce spam without harming normal user experience.
##### Question
Without a classifier table, what alternative metrics would you track to monitor spam and overall user experience? If report rate declines, what potential causes could explain it and what extra metrics would you examine? When running an anti-spam A/B test where spammers are rare, how would you select test and control groups?
##### Hints
Consider message volume, unique senders, report-per-message, acceptance rate, stratified sampling, power.
Quick Answer: This interview question evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer for Design Metrics to Track and Analyze Spam Impact states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
A messaging product team wants to reduce spam without harming normal user experience. You do not have access to a ground-truth spam classifier table.
Tasks
Metrics without a classifier: What proxy metrics would you track to monitor spam prevalence and overall user experience?
Interpreting a decline: If the user report rate (reports per message) declines, what plausible causes could explain it, and what additional metrics would you examine to disambiguate?
Experiment design with rare spammers: When running an anti-spam A/B test where spammers are rare, how would you select test and control groups to ensure power and minimize interference?
Hint: Consider message volume, unique senders, reports per message, acceptance rate of message requests, stratified sampling, and power.
Constraints & Assumptions
Preserve the scope, facts, inputs, and requested outputs from the prompt above.
If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.
Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.
Clarifying Questions to Ask Guidance
Clarify the business objective, unit of analysis, time window, exposure definition, and primary metric.
State assumptions about instrumentation, randomization, sample size, and data quality.
Separate descriptive analysis from causal claims.
What a Strong Answer Covers Guidance
A metric framework with primary, guardrail, and diagnostic metrics.
A credible analysis or experiment design with clear assumptions and bias checks.
SQL/statistical logic for segmentation, variance, confidence, and data validation where relevant.
An actionable recommendation that explains trade-offs and next steps.
Follow-up Questions Guidance
What sanity checks would you run before trusting the result?
How would you handle novelty effects, seasonality, or selection bias?