Find the Probability That Two Uniform Variables Have Product Above One-Half

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Quick Overview

Compute the probability that two independent uniform variables have product above one-half by conditioning or integrating over the unit square.

Find the Probability That Two Uniform Variables Have Product Above One-Half

Company: Squarepoint

Role: Data Scientist

Category: Statistics & Math

Difficulty: medium

Interview Round: Technical Screen

Let `X` and `Y` be independent random variables, each uniformly distributed on the interval `(0, 1)`. What is the probability that `X * Y > 1/2`? ### Constraints and Clarifications Use the continuous uniform distribution and the given independence. Explain the relevant region or conditional probability and give an exact expression. The distinction between strict and non-strict inequality at the boundary has probability zero here. ```hint Locate the feasible part of the square For a fixed value of `X`, determine which values of `Y` can satisfy the product inequality and when that interval is nonempty. ``` ### What a Strong Answer Covers - The uniform joint density on the unit square and the product-inequality region. - Correct integration limits rather than integrating over impossible values of `X`. - An exact probability, a reasonable numerical interpretation, and a simple bound that checks the result. ### Follow-up Questions 1. How does the expression change for `P(X * Y > t)` with `0 < t < 1`? 2. Why is multiplying `P(X > 1/2)` and `P(Y > 1/2)` not the answer to the original question?

Overview: Compute the probability that two independent uniform variables have product above one-half by conditioning or integrating over the unit square.

Read the full Squarepoint Data Scientist interview experience this question came from

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Sep 9, 2026
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Let X and Y be independent random variables, each uniformly distributed on the interval (0, 1). What is the probability that X * Y > 1/2?

Constraints and Clarifications

Use the continuous uniform distribution and the given independence. Explain the relevant region or conditional probability and give an exact expression. The distinction between strict and non-strict inequality at the boundary has probability zero here.

What a Strong Answer Covers Guidance

  • The uniform joint density on the unit square and the product-inequality region.
  • Correct integration limits rather than integrating over impossible values of X .
  • An exact probability, a reasonable numerical interpretation, and a simple bound that checks the result.

Follow-up Questions Guidance

  1. How does the expression change for P(X * Y > t) with 0 < t < 1 ?
  2. Why is multiplying P(X > 1/2) and P(Y > 1/2) not the answer to the original question?
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