Balance of Arms
A hard SQL mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- SQL
- Difficulty
- hard
- Seniority
- L4
Interview Prompt
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.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your sql solution with real code execution
- Get instant feedback and a hire/no-hire decision