Explain instrumental variables with an example
Last updated: February 1, 2026
Quick Overview
Explain instrumental variables in simple terms and provide a concrete example.
HubSpot
February 1, 2026213
7
2,723 solved
Explain instrumental variables in simple terms and provide a concrete example.
HubSpot values data-driven decision making. This Technical Screen 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
- State the correct formula or theorem with clear definitions
- Apply the concept to the given scenario step by step
- Interpret the result in plain language
- Identify assumptions and when they might be violated
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
- How would you design a follow-up experiment based on these results?
- How would you handle multiple comparisons?
- What if the sample size is very small?
- What alternative statistical method could you use here?
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Problem Formulation
In causal inference, instrumental variables (IV) are used when we suspect that an independent variable (X) is correlated with the error term in a regression model, leading to biased estimates of the e...
Solution Approach
To leverage instrumental variables, we follow these steps:
- Identify the Instrument: Choose a variable Z that meets the two conditions outlined above.
- Two-Stage Least Squares (2SLS): ...
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