Balance of Arms

A hard SQL interview practice problem on DataDriven. Write and execute real sql code with instant grading.

Domain

SQL

Difficulty

hard

Seniority

L4

Problem

An experimentation platform needs to confirm each test's groups are balanced before readout, and treats every arm that is not the control group as treatment. For each experiment, find the unique users in control, the unique users in treatment, and the treatment-to-control ratio, leaving the ratio empty when an experiment has no control users.

Summary

Every test has two sides. Count who actually landed on each.

Practice This Problem

Solve this SQL problem with real code execution. DataDriven runs your SQL queries against a real database and grades it automatically.