Common Probability Interview Questions for data scientists

Common Probability Interview Questions for data scientists, here is a collection of statistics and probability interview questions and some sample solutions.

If you are preparing for a data scientist job interview and want to practice mock interviews with FAANG hiring managers, feel free to use our coaching service.

If you have questions, or want to share your answers, discuss in our forum.

Ads Serving:

There are two different ads serving mechanisms for the newsfeed. 

The first is randomly replacing a feed with an advertisement with a probability of 4%. 

The second is: every 25 feeds, turn one of them into an ad.

Question 1: What is the expected number of ads shown in 100 news stories for each option? Variance? 

Sample Answer:

1. Binomial distribution: p=0.04, n=100, E= np = 4, V=n*p*(1-p) =3.84 
2. E=4, V=0 

Question 2: Probability of seeing more than twice of expected value times of ads

Sample Answer: 1-p(x<=8) 

Question 3: What is the maximum number of back to back ads 

Question 4: What is the expected number of back-to-back ads

Question 5: What is the probability of showing back-to-back ads.

Conference Rooms

There are N conference rooms, and M meetings are randomly assigned to each room.

Question: If we already know that room #1 has been assigned at least one meeting, what is the expected number of meetings that were assigned to room #1?

Drawing a user

Question 1. 1000 people, each time we select 10 users with replacement, on average, how many times before a specific user is drawn?

Question 2: 1000 people, each time we select 10 users without replacement, on average, how many times before a specific user is drawn?

Fake news

About 2% of news is fake news, 98% are non-fake news. There is a fake news detection model with 95% accuracy of correctly identifying either fake or non-fake news. 

Question: What is the actual probability if a piece of news is predicted as fake news?

Daily comments distribution

Question 1: Every day, we count the total number of comments on a forum. What is the daily number of comments distribution that may look like?

Question 2: draw the distribution on a whiteboard

Ads reviewer 

20% of reviewers are lazy reviewers who always approve an ad without carefully reviewing them.

80% of reviewers are good reviewers who give 60% of ads approvals and 40% rejections.

Q1: The overall probability of a new ad being approved.

Q2: If an ad is rejected, what is the probability that it's reviewed by a lazy reviewer?

Q3: Expected number of approved ads every 100 ads.

Q4: A reviewer gave 3 good reviews, probability of them being a lazy reviewer

Common Probability Interview Questions for data scientists, here is a collection of statistics and probability interview questions and some sample solutions.

If you are preparing for a data scientist job interview and want to practice mock interviews with FAANG hiring managers, feel free to use our coaching service.

If you have questions, or want to share your answers, discuss in our forum.