Calculate expected value for click-through rates
Last updated: April 16, 2026
Quick Overview
Given the following scenario about user conversion, calculate the the sample size needed.
Instacart
April 16, 202661
6
1,085 solved
Given the following scenario about user conversion, calculate the the sample size needed.
Instacart asks this during the Technical Screen 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 you discover a bug in the logging during the experiment?
- What would you do if a stakeholder wants to end the experiment early because initial results look good?
- How would you handle seasonality in your experiment?
- How would you handle interference between treatment and control?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Browse Analytics QuestionsSample Answer
Problem Setup
The analytical question here is to estimate the sample size needed to achieve a statistically significant result for click-through rates (CTR) on Instacart's platform. To do this, we need historical d...
Methodology
We will use the formula for sample size calculation for comparing two proportions, which is appropriate for this scenario where we are interested in the difference in CTR between two groups (control v...
Submit Your Answer
