Compute p-values for 2 variants vs control

Quick Overview

This question evaluates a candidate's competence in statistical hypothesis testing and experiment analysis, focusing on A/B/n comparison of conversion rates, p-value computation, confidence interval estimation for lift, multiple-testing considerations, and interpretation of results.

Compute p-values for 2 variants vs control

Company: Gusto

Role: Data Scientist

Category: Analytics & Experimentation

Difficulty: easy

Interview Round: Technical Screen

## A/B/n test: compute p-values and make a ship decision You ran an online A/B/n experiment with **1 control** and **2 treatment variants** (A/B/C). You are given a table of aggregated results with one row per group: **Table: `ab_results`** - `group` (STRING): one of `control`, `variant_1`, `variant_2` - `users` (INT): number of unique users exposed to the group - `conversions` (INT): number of users who converted (binary outcome) Assume: - Users are independently assigned and each user appears in exactly one group. - The metric is **conversion rate** = `conversions / users`. - You want to test whether each variant changes conversion rate vs control. - Use a two-sided test unless you justify a one-sided test. ### Tasks 1. Using Python, compute the **p-value** for: - `variant_1` vs `control` - `variant_2` vs `control` (State what statistical test you chose and why.) 2. Provide **95% confidence intervals** for the lift (difference in conversion rates) for each variant vs control. 3. Because there are **two** comparisons vs the same control, explain how you would handle **multiple testing** (e.g., Bonferroni, Holm, FDR), and how that affects your decision. 4. Interpret the results in plain language and recommend **ship / no-ship** (and under what conditions you’d run a follow-up experiment). Include any assumptions or caveats (e.g., sample size adequacy, novelty effects, missing data, metric definition issues).

Quick Answer: This question evaluates a candidate's competence in statistical hypothesis testing and experiment analysis, focusing on A/B/n comparison of conversion rates, p-value computation, confidence interval estimation for lift, multiple-testing considerations, and interpretation of results.

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Nov 2, 2025, 12:00 AM
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A/B/n test: compute p-values and make a ship decision

You ran an online A/B/n experiment with 1 control and 2 treatment variants (A/B/C).

You are given a table of aggregated results with one row per group:

Table: ab_results

  • group (STRING): one of control , variant_1 , variant_2
  • users (INT): number of unique users exposed to the group
  • conversions (INT): number of users who converted (binary outcome)

Assume:

  • Users are independently assigned and each user appears in exactly one group.
  • The metric is conversion rate = conversions / users .
  • You want to test whether each variant changes conversion rate vs control.
  • Use a two-sided test unless you justify a one-sided test.

Tasks

  1. Using Python, compute the p-value for:
    • variant_1 vs control
    • variant_2 vs control (State what statistical test you chose and why.)
  2. Provide 95% confidence intervals for the lift (difference in conversion rates) for each variant vs control.
  3. Because there are two comparisons vs the same control, explain how you would handle multiple testing (e.g., Bonferroni, Holm, FDR), and how that affects your decision.
  4. Interpret the results in plain language and recommend ship / no-ship (and under what conditions you’d run a follow-up experiment).

Include any assumptions or caveats (e.g., sample size adequacy, novelty effects, missing data, metric definition issues).

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