Intuit·Data Scientist·Technical Phone Screen
Jul 2026
Intuit data scientist interview that went deep on A/B testing statistics, like really deep. They wanted full derivations, not just 'run a z-test and move on,' so if you're fuzzy on where the z-test formula actually comes from, this round will find that out fast.
- For an A/B test on a binary delivery outcome, which significance test would you use and why is it preferable to a t-test on proportions? Derive the test statistic from first principles starting from the Bernoulli distribution through to the normal approximation, and state the conditions under which that approximation holds.
- Using the large-sample A/B test data (control: 920/1000 delivered, variant: 880/1000 delivered), compute the p-value to three significant figures and a 95% confidence interval for the difference in proportions. Show your work.
- A small-market rollout gives you much smaller sample sizes: 20 out of 25 delivered in control, 12 out of 18 in variant. How does your test choice change? Walk through whether you'd use chi-square, Fisher's exact, or a z-test, and either compute the exact p-value or explain precisely how you'd get it.
- When does a two-sample t-test produce essentially the same result as a z-test for proportions, and when does it break down? Give at least two concrete failure modes.
“This is where I spent most of my mental energy.” The rest of the author's notes on Data Scientist interview at Intuit, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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