Calculate probability for A/B test results
Last updated: September 30, 2025
Quick Overview
Given the following scenario about user conversion, calculate the the p-value.
Confluent
September 30, 20256
5
4,737 solved
Given the following scenario about user conversion, calculate the the p-value.
Confluent asks this during the Onsite to assess your experimentation skills. They want to see how you define success metrics, design controlled experiments, and interpret results with appropriate statistical rigor.
What the Interviewer Expects
- Design a rigorous experiment with proper randomization and sample size calculation
- Define primary and guardrail metrics with clear rationale
- Address novelty effects, network effects, and interference
- Segment results appropriately and identify heterogeneous treatment effects
- Propose follow-up analyses when results are ambiguous
Key Topics to Cover
How to Approach This
- Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
- Run experiments long enough to account for novelty effects and weekly seasonality.
- Use funnel analysis to identify where users drop off for maximum optimization impact.
- Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
- Consider network effects and interference between treatment and control groups.
Possible Follow-up Questions
- What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
- What if you discover a bug in the logging during the experiment?
- How would you handle interference between treatment and control?
- How would you handle an experiment where the control and treatment groups are different sizes?
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Browse Analytics QuestionsSample Answer
Problem Setup
The analytical question here is: "What is the p-value indicating whether there is a statistically significant difference in user conversion rates between the control group and the treatment group in a...
Methodology
To calculate the p-value, I would use a two-proportion z-test since we are comparing conversion rates between two independent groups. The steps are as follows:
- Calculate the conversion rates for bo...
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