Determine Probability of Friend Request Being Fake
Company: Meta
Role: Data Scientist
Category: Statistics & Math
Difficulty: easy
Interview Round: Onsite
##### Scenario
Probability that an incoming friend request is from a fake account
##### Question
95% of accounts are real, 5% fake; fake accounts send 10× more friend requests than real ones. If you receive a friend request, what is the probability it is from a fake account?
##### Hints
Apply Bayes’ theorem: posterior ∝ prior × likelihood.
Overview: Determine Probability of Friend Request Being Fake evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Community answers
Answer by SS
10⋅0.05+1⋅0.9510⋅0.05
=0.50.5+0.95=0.51.45≈0.3448= \frac{0.5}{0.5 + 0.95}
= \frac{0.5}{1.45}
\approx 0.3448=0.5+0.950.5=1.450.5≈0.3448