Compute posterior fake probability using Bayes' rule

Quick Overview

The problem evaluates understanding of Bayes' rule and conditional probability within the Statistics & Math domain for a Data Scientist role, at an introductory applied probability/interpretation level.

Compute posterior fake probability using Bayes' rule

Company: Meta

Role: Data Scientist

Category: Statistics & Math

Difficulty: medium

Interview Round: Technical Screen

A platform runs an automated detector to flag fake accounts. - Prior probability an account is fake: \(P(F)=0.02\). - True positive rate (sensitivity): \(P(\text{Flag}\mid F)=0.90\). - False positive rate: \(P(\text{Flag}\mid\neg F)=0.05\). If an account is flagged, what is the probability it is actually fake, \(P(F\mid \text{Flag})\)? Show your calculation.

Overview: The problem evaluates understanding of Bayes' rule and conditional probability within the Statistics & Math domain for a Data Scientist role, at an introductory applied probability/interpretation level.

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Oct 14, 2025
mediumData ScientistTechnical ScreenStatistics & Math
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A platform runs an automated detector to flag fake accounts.

  • Prior probability an account is fake: P(F)=0.02P(F)=0.02 .
  • True positive rate (sensitivity): P(FlagF)=0.90P(\text{Flag}\mid F)=0.90 .
  • False positive rate: P(Flag¬F)=0.05P(\text{Flag}\mid\neg F)=0.05 .

If an account is flagged, what is the probability it is actually fake, P(FFlag)P(F\mid \text{Flag})? Show your calculation.

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