N+A Data Scientist Interview Questions and Answers for Experienced

Q1. Difference between CNN and MLP
Ans. 
CNN is used for image recognition while MLP is used for general classification tasks.
• CNN uses convolutional layers to extract features from images while MLP uses fully connected layers.

• CNN is better suited for tasks that require spatial understanding like object detection while MLP is better for tabular data.

• CNN has fewer parameters than MLP due to weight sharing in convolutional layers.

• CNN can handle input of varying
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Q1. Work done in previous companty
Ans. 
Developed machine learning models to predict customer churn and optimize marketing campaigns.
• Built predictive models using Python and scikit-learn

• Utilized SQL to extract and manipulate data for analysis

• Collaborated with cross-functional teams to implement data-driven solutions
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I was asked Python, sql, coding questions

Case study on how would you identify the total number of footfall on a airport

Q1. ML concepts , regression, regularization etc
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Q1. Self Intro and projects discussion
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Q2. Feature selection methods
Ans. 
Feature selection methods help in selecting the most relevant features for building predictive models.
• Feature selection methods aim to reduce the number of input variables to only those that are most relevant.

• Common methods include filter methods, wrapper methods, and embedded methods.

• Examples include Recursive Feature Elimination (RFE), Principal Component Analysis (PCA), and Lasso regression.
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Round duration - 60 Minutes
Round difficulty - Easy

Round duration - 60 Minutes
Round difficulty - Easy

There were 10 MCQs ranging from Aptitude to Programming MCQs to basics of Data Science.
The coding question only the optimized solution was accepted

Q1. 
Special Sum of Array Problem Statement
Given an array 'arr' containing single-digit integers, your task is to calculate the total sum of all its elements. However, the resulting sum must also be a single-...read more
Ans. 
Calculate the total sum of array elements until a single-digit number is obtained by repeatedly summing digits.
• Iterate through the array and calculate the sum of all elements.

• If the sum is a single-digit number, return it. Otherwise, repeat the process of summing digits until a single-digit number is obtained.

• Return the final single-digit sum.
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Round duration - 45 minutes
Round difficulty - Easy

The interview happened in the evening. It was an online video call.
The interviewer was very cooperative. I would say it was rather a discussion session between us.

Q1. 
Clone a Linked List with Random Pointers
Given a linked list where each node contains two pointers: one pointing to the next node and another random pointer that can point to any node within the list (or ...read more
Ans. 
Create a deep copy of a linked list with random pointers.
• Iterate through the original linked list and create a new node for each node in the list.

• Store the mapping of original nodes to new nodes in a hashmap to handle random pointers.

• Update the random pointers of new nodes based on the mapping stored in the hashmap.

• Return the head of the copied linked list.
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Round duration - 10 Minutes
Round difficulty - Easy

It was late night
It was a telephonic call

Q1. How to extract numbers pre decimal point from a long list of decimalnumbers with efficiency
Ans. 
Use string manipulation to efficiently extract numbers before the decimal point from a list of decimal numbers.
• Split each decimal number by the decimal point and extract the number before it

• Use regular expressions to match and extract numbers before the decimal point

• Iterate through the list and extract numbers using string manipulation functions
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Q1. Central Limit Theorem
Ans. 
Central Limit Theorem states that the sampling distribution of the sample mean approaches a normal distribution as the sample size increases.
• The Central Limit Theorem is essential in statistics as it allows us to make inferences about a population based on a sample.

• It states that regardless of the shape of the population distribution, the sampling distribution of the sample mean will be approximately normally distribut...read more
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