ffreedom app Data Science Intern Interview Questions and Answers

Categories of the CAT exam include Quantitative Aptitude, Verbal Ability, Data Interpretation and Logical Reasoning, and Graphical questions.

Medium level. Focus on SQL subqueries application.

Q1. Statistical questions related to different hypothesis testing
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Q2. Questions related to different machine learning model
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Round duration - 60 minutes
Round difficulty - Easy

Timing: 8:00-9:00 PM
There was 1 MCQ and 3 SQL queries. The platform was easy to use and navigate.

Q1. SQL Question
A table containing the details of all the drivers, and another table containing the details of trips is provided. Query the name of drivers that have taken at least 1 trip.
Ans. 
Step 1 : I performed inner join on the 2 tables on the driver_id key. 
Step 2 : Then I selected the distinct driver_name 's from the joined table. 
Step 3 : This query was satisfying all the 5 test cases.
Answered by CodingNinjas
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Q2. SQL Question
A table containing the details of all the drivers, and another table containing the details of trips is provided. Query the name and number of trips taken by each driver which has rating more t...read more
Ans. 
Step 1 : I performed inner join on the 2 tables on the driver_id key. 
Step 2 : Then I performed group by on the driver_id, and selected the name and COUNT(trip_id). I filtered out the trips with rating less than 4 by using "WHERE trip_rating>4".
Step 3 : This query was satisfying all the 5 test cases.
Answered by CodingNinjas
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Q3. SQL Question
A table containing the details of Uber employees were provided. I had to query the maximum number of employees that worked in the company during each employee's tenure.
Ans. 
I did not have enough time to think about this question, and could not solve it. I submitted a blank response for this question.
Answered by CodingNinjas
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Round duration - 30 minutes
Round difficulty - Medium

Timing: 11 AM-11:30 AM
The interviewer was very kind and helpful. He helped me by giving hints whenever I was stuck.

Q1. SQL Question
User table containing user_id, ph_no, email_id, signup_city, banned, role, timestamp and trips table containing trip_id, client_id, driver_id, city_id, product_id, request_at, status={completed...read more
Ans. 
Step 1 : Get the month and year from the request_at variable which is in timestamp format.
Step 2 : Select COUNT(trip_id) to get the number of trips
Step 3 : Put the WHERE condition to get only the trips of January 2021.
Answered by CodingNinjas
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Q2. SQL Question
User table containing user_id, ph_no, email_id, signup_city, banned, role, timestamp and trips table containing trip_id, client_id, driver_id, city_id, product_id, request_at, status={completed...read more
Ans. 
Step 1 : Join the 2 tables on trips.client_id=User.user_id
Step 2 : Select COUNT(DISTINCT trip_id) to get the number of trips
Step 3 : Put the WHERE condition to get only the trips where user has role='RIDER'.
Answered by CodingNinjas
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Q3. SQL Question
User table containing user_id, ph_no, email_id, signup_city, banned, role, timestamp and trips table containing trip_id, client_id, driver_id, city_id, product_id, request_at, status={completed...read more
Ans. 
Step 1 : Join the 2 tables on trips.client_id=User.user_id
Step 2 : Use CASE WHEN statement to get 0 and 1 for successful and unsuccessful trips respectively.
Step 3 : Take ratio of unsuccessful trip by total trips to get the proportion of unsuccessful trips.
Step 4 : Get the month and year from the request_at variable which is in timestamp format.
Step 5 : Put the WHERE condition to get only the trips of January 2021.
Answered by CodingNinjas
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Round duration - 30 minutes
Round difficulty - Medium

Timing: 12:15 PM to 12:45 PM.
The interviewer was very helpful and friendly. He was more interested in my approach rather than the final answer.

Q1. Puzzle Question
In a bank, suppose there are 5 counters. Which approach mentioned below is better?
1) The new customer goes to whichever counter has a smaller queue
2) Each counter has a specific purpose (e.g...read more
Ans. 
Tip 1 : Clarify the question properly if you have any doubts
Tip 2 : Try to think of out of the box solutions
Answered by CodingNinjas
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Q2. Puzzle Question
What new feature would you like to add in Uber?
Ans. 
Tip 1 : Creativity has no limit in such questions
Tip 2 : Suggest any of the dreams that you would like to see in your dream company
Tip 3 : I suggested ideas such as Uber Ambulance, Uber Flights, etc
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Round duration - 30 minutes
Round difficulty - Hard

Timing: 3:00PM to 3:30PM
This was Hiring Manager round. He asked me case study type of questions.

Q1. Puzzle Question
How would you predict which user is likely to churn in the next 1 month? What variables would you consider for this?
Ans. 
Tip 1 : Thoroughly understand the question
Tip 2 : Ask questions about the existing approach that is used by the company
Tip 3 : Try to answer from a technical, as well as business point of view.
Answered by CodingNinjas
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Q1. Questions on Past Project
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Q2. SQL Dense Rank - also having the option to do in Pandas
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Q3. Pandas groupby on a dataset given - required to calculate group wise yoy rate of a column
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Q1. Past project ( which he chose , he chose my very first project , which I had forgotten) so ended up screwing it
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Q2. SQL / Pyspark question - difficult question
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Q1. Tell me about your projects?
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Q2. How do you approach the project if you are using logistic regression model?
Ans. 
Approach involves data preprocessing, model training, evaluation, and interpretation.
• Perform data preprocessing such as handling missing values, encoding categorical variables, and scaling features.

• Split the data into training and testing sets.

• Train the logistic regression model on the training data.

• Evaluate the model using metrics like accuracy, precision, recall, and F1 score.

• Interpret the model coefficients to under...read more
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Q1. What are you future goals?
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Q2. What would you do if your interested field doesnt have any work in the company?
Ans. 
I would seek opportunities to apply my skills in related fields within the company.
• Explore other departments or teams within the company that may have projects related to my field of interest

• Offer to collaborate with colleagues in different departments to bring a new perspective to their projects

• Seek out professional development opportunities to expand my skills and knowledge in related areas
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Questions related to basic coding were asked, and some background on projects and discussions alongside maths and statistics concepts

Q1. Questions related to projects done at my previous company
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Q1. Questions related to my work at previous company
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Q2. ML system design use case type of discussion
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Q1. Explain TFIDF and explain CNN
Ans. 
TFIDF is a technique to quantify the importance of a word in a document. CNN is a deep learning algorithm commonly used for image recognition.
• TFIDF stands for Term Frequency-Inverse Document Frequency and is used to evaluate the importance of a word in a document relative to a collection of documents.

• TFIDF is calculated by multiplying the term frequency (number of times a word appears in a document) by the inverse docu...read more
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Q2. Mysql window functions and exceute same in pandas
Ans. 
Window functions in MySQL and pandas are used for performing calculations across a set of rows related to the current row.
• In MySQL, window functions can be used with OVER() clause to perform calculations like ranking, cumulative sum, moving average, etc.

• In pandas, window functions can be applied using the rolling() and expanding() methods to calculate statistics over a specified window of rows.

• Example: In MySQL, to cal...read more
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Q1. Asked firstly some question over my resume then 2 case study type problems where i have to improve the recommdation system for zomato, and finally one coding question based on two pointer
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Q1. Breadth of data science, Linear algebra, prob&stats, Lin reg, Log reg, DT, RF
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Q1. Grilled in Mathematics behind Lin Reg, closed form solution, scalebility of lin reg
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Q1. System design, took a project from my resume and asked me to design the whole solution. Project was a chatbot
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