The suspicious signup spike

A root cause analysis question from a product manager interview, set at Rankoli, a fictional test prep company.

The question

Skills this case tests

A starting metric tree

Weekly signups = organic + paid + referral; then quality: signups × day-1 activation × paid conversion

How to approach this case

Before agreeing to double down, define success. Is a signup the goal, or an active learner who later pays? Ask how a signup is counted and over what window, then check the data is clean. Split signups by source to see where the extra volume came from. Then judge quality, not only volume: activation in the first day and paid conversion for each source and cohort. Ask what changed recently in each channel, including marketing, onboarding and any rewards. Look at who is driving the growth: many users each bringing a little, or a few bringing a lot? Use any holdout group as your control. A strong close answers the CEO directly, says what to change before spending more, and gives a metric that rewards real learners rather than raw signups.

The full method for root cause analysis questions · A worked example answer

After the mock interview you get scores on five skills, what to fix with quotes from your answers, and the ideal path for this case.