Interpret a statistically significant lift of 2% from an experiment
Last updated: August 18, 2025
Quick Overview
An experiment shows conflicting results. What conclusions can you draw? What are the caveats?
DoorDash
August 18, 202542
5
699 solved
An experiment shows conflicting results. What conclusions can you draw? What are the caveats?
DoorDash values data-driven decision making. This Onsite question assesses whether you can design experiments, interpret results correctly, and avoid common statistical pitfalls like p-hacking or Simpson's paradox.
What the Interviewer Expects
- Set up the problem formally with proper notation
- Apply the correct statistical test with clear justification
- Interpret results with appropriate caveats and confidence levels
- Discuss practical significance vs statistical significance
- Identify potential confounders and how to address them
Key Topics to Cover
How to Approach This
- Define your hypotheses (H0 and H1) clearly before performing any test.
- Calculate required sample size BEFORE running an experiment, using power analysis.
- Remember the Central Limit Theorem: sample means become approximately normal with large n.
- Watch for Simpson's paradox. Always segment data by key dimensions.
- Distinguish between statistical significance and practical significance.
Possible Follow-up Questions
- What alternative statistical method could you use here?
- What if the sample size is very small?
- How would you design a follow-up experiment based on these results?
- How would you explain this result to a non-technical audience?
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Browse Statistics QuestionsSample Answer
Problem Formulation
To analyze the 2% lift reported from the experiment, we start by defining our null hypothesis (H0) and alternative hypothesis (H1).
- H0: The new intervention (e.g., a promotional offer) does no...
Solution Approach
To determine if the observed 2% lift is statistically significant, we will perform a hypothesis test using the following steps:
- Data Collection: Gather data from both control and experimental g...
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