Business Context

Learnly is a mobile learning app with daily lessons, quizzes, and streaks. The product team is reviewing a 12-week engagement chart after a recent home feed redesign and wants a clear readout of the main takeaway, not just a description of the line moving up or down.

Metric Scenario

The chart shows weekly active users (WAU), average sessions per active user, and 4-week retention from Week 1 to Week 12. WAU rises from 420,000 in Week 1 to 510,000 in Week 8, then falls to 470,000 by Week 12. Sessions per active user stay near 4.8 through Week 6, drop to 4.1 in Week 9, and recover slightly to 4.3 by Week 12. Meanwhile, 4-week retention declines steadily from 38% in Week 1 to 31% in Week 12. A campaign launched in Week 4 increased new-user signups by 22%, and the redesign shipped in Week 7.

Stakeholders ask: Is engagement actually improving, flat, or deteriorating? What is the single most important takeaway from the chart, and what follow-up analysis would you do next?

Requirements

1. Define how you would read the chart before jumping to conclusions.
2. State the main takeaway in 2-3 sentences for an executive audience.
3. Identify whether the change is more likely driven by acquisition, depth of engagement, or retention.
4. Propose a metric decomposition to validate your conclusion.
5. List the most important caveats or chart-reading pitfalls.

Data Available

• weekly_kpi_summary: week_start, wau, dau, sessions, lessons_completed, new_signups
• user_activity: user_id, event_date, session_id, lesson_id, device_type, country
• user_cohorts: user_id, signup_date, acquisition_channel, app_version
• retention_summary: cohort_week, week_n_retained_users, cohort_size