Novelty Effect Detection Week-by-Week

SQLHardSenior levelMicrosoft~15 min

Problem

**[Asked at Microsoft]**

Detect if a treatment shows the **novelty effect** — a large initial lift that
decays over time.

For each week, return the absolute effect (`treatment - control`) and the
lift percentage. Order by week.

Example rows — the live problem includes the full dataset.

ab_weekly

week	variant	metric_value

Your answer should return 4 rows with the columns week, effect_size, lift_pct.

SELECT *
FROM ab_weekly;

Write SQL and run it instantly in your browser — even on your phone. No signup needed to try.

Create a free account to unlock the optimal solution, a step-by-step explanation, and the hidden test cases that grade your answer.