Compute conditional occupancy across two rooms

Quick Overview

This question evaluates a data scientist's understanding of conditional probability and Bayesian updating, testing probabilistic reasoning and inference about joint occupancy states.

Compute conditional occupancy across two rooms

Company: Meta

Role: Data Scientist

Category: Statistics & Math

Difficulty: easy

Interview Round: Onsite

Two rooms may be occupied with the following priors: with probability 1/3 both rooms are occupied, with probability 1/3 exactly one room is occupied, and with probability 1/3 both are empty. You pick a room uniformly at random to check. (a) What is the probability the room you check is occupied? (b) Given you find your chosen room occupied, what is the probability the other room is also occupied? Show the Bayes calculation.

Quick Answer: This question evaluates a data scientist's understanding of conditional probability and Bayesian updating, testing probabilistic reasoning and inference about joint occupancy states.

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Oct 13, 2025, 9:49 PM
easyData ScientistOnsiteStatistics & Math
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Probability and Bayes Update: Two Rooms

Setup

There are two rooms. Prior over occupancy states:

  • With probability 1/3: both rooms are occupied.
  • With probability 1/3: exactly one room is occupied.
  • With probability 1/3: both rooms are empty.

You pick one room uniformly at random to check.

Tasks

(a) What is the probability the room you check is occupied?

(b) Given you find your chosen room occupied, what is the probability the other room is also occupied? Show the Bayes calculation.

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