Upstart·Data Scientist·Onsite - Multi Round
May 2026
Onsite stats and probability round for a research-scientist-adjacent data science role at Upstart. Two questions, both pretty theoretical, and the second one had a Bayesian twist I wasn't fully expecting in what felt like a standard frequentist setup.
- Given the data-generating process y = X + ε where X and ε are independent standard normals, what happens if you flip it and regress X on y using OLS? Derive the regression coefficient.
- A sample of 100 children from a village shows 50 from 1-child families, 30 from 2-child families, and 20 from 3-child families. Estimate the proportion of 1-child families, build a 95% confidence interval for it, and then explain how you'd get an exact credible interval using a Dirichlet prior on the family-size proportions.
“This one got me for a second because my instinct was to just say 0.5 and move on, but they wanted the full derivation.” The rest of the author's notes on Data Scientist interview at Upstart, Onsite - Multi Round round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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