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Determine Posterior Probability of Bad User Prediction

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's understanding of Bayesian reasoning and conditional probability, focusing on concepts such as prevalence, sensitivity, specificity, and posterior probability in classifier evaluation within the Statistics & Math domain.

  • easy
  • Meta
  • Statistics & Math
  • Data Scientist

Determine Posterior Probability of Bad User Prediction

Company: Meta

Role: Data Scientist

Category: Statistics & Math

Difficulty: easy

Interview Round: Onsite

##### Scenario Evaluating a classifier that flags bad actors ##### Question 5 % of users are actually bad. The model labels a user correctly with 95 % accuracy for both classes. If the model predicts a user is bad, what is the posterior probability the user is truly bad? ##### Hints Direct application of Bayes’ rule with symmetric 95 % true-positive and false-positive complements.

Quick Answer: This question evaluates a candidate's understanding of Bayesian reasoning and conditional probability, focusing on concepts such as prevalence, sensitivity, specificity, and posterior probability in classifier evaluation within the Statistics & Math domain.

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Meta
Jul 12, 2025, 6:59 PM
Data Scientist
Onsite
Statistics & Math
32
0

Evaluating a Classifier That Flags Bad Actors

Question

You are evaluating a binary classifier for detecting bad actors among users.

Given:

  • Prevalence: 5% of users are truly bad.
  • Model performance: 95% sensitivity (true-positive rate) and 95% specificity (true-negative rate).

If the model predicts a user is bad, what is the posterior probability that the user is truly bad?

Solution

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