In the magical world of the Walt Disney Company, where creativity meets cutting-edge technology, data science and analytics play a pivotal role in creating unforgettable experiences for audiences worldwide. If you find yourself embarking on the exciting journey of interviewing for a data-related role at Disney, it’s essential to be well-prepared. To help you on this quest, let’s dive into some common interview questions and concise yet insightful answers you might encounter.
Table of Contents
Technical Interview Questions
Question: What’s the difference between left join and right join in SQL?
Answer:
LEFT JOIN:
- Includes all records from the left table.
- Includes matching records from the right table.
- Non-matching records from the right table are filled with NULLs.
RIGHT JOIN:
- Includes all records from the right table.
- Includes matching records from the left table.
- Non-matching records from the left table are filled with NULLs.
Question: What is the K-Means algorithm?
Answer: K-Means is an unsupervised machine learning algorithm used for clustering data points into groups based on similarities. It works by iteratively assigning each data point to the nearest cluster center and then updating the cluster centers based on the mean of the data points in each cluster. This process continues until the cluster centers no longer change significantly, or a specified number of iterations is reached. The goal is to minimize the sum of squared distances between data points and their respective cluster centers.
Question: Explain the pros and cons of different machine learning models.
Answer:
Linear Regression:
- Pros: Simple, fast, good for linear relationships.
- Cons: Assumes linearity, sensitive to outliers, limited complexity.
Decision Trees:
- Pros: Easy to interpret, handles numerical and categorical data, feature selection.
- Cons: Prone to overfitting, instability, and struggles with linear relationships.
Support Vector Machines (SVM):
- Pros: Effective in high dimensions, versatile kernels, robust to overfitting in high-dimensional space.
- Cons: Computationally expensive, difficult to interpret, not suited for large datasets.
Random Forest:
- Pros: High accuracy, good for high dimensions, resistant to overfitting.
- Cons: Slow prediction time, harder to interpret, more computational resources.
Neural Networks:
- Pros: High performance on complex problems, learns intricate patterns, versatile data handling.
- Cons: Needs large data, prone to overfitting, computationally intensive.
Naive Bayes:
- Pros: Simple, efficient, good for small datasets.
- Cons: Assumes feature independence, poor complexity handling, and can be outperformed by more complex models.
Question: Explain A/B testing.
Answer: A/B testing is a comparison method where two versions (A and B) are tested against each other to identify which performs better on a given metric. Users are randomly divided into two groups to experience either version. The outcome is analyzed statistically to determine if there’s a significant difference in performance, guiding data-driven decisions to improve products or strategies.
Question: Describe Time series forecasting.
Answer: Time series forecasting involves using historical data to predict future values in a sequence over time. This process analyzes patterns, trends, and cycles in past data to forecast future events, such as stock prices, weather conditions, or sales trends. Techniques range from simple models like moving averages to complex ones like ARIMA (AutoRegressive Integrated Moving Average) and machine learning models. The goal is to make informed decisions by anticipating future values in the series.
Question: Describe regression.
Answer: Regression is a statistical method used to model the relationship between a dependent variable and one or more independent variables. The main goal is to understand how changes in the independent variables affect the dependent variable. This technique is widely used for prediction and forecasting, where the output can be a continuous quantity (like house prices or temperatures).
Data Structure Interview Questions
Question: What is a data structure?
Answer: A data structure is a particular way of organizing and storing data in a computer so that it can be accessed and modified efficiently. Different types of data structures are suited to different kinds of applications, and some are highly specialized for specific tasks.
Question: Explain the difference between an array and a linked list.
Answer: An array is a collection of elements stored at contiguous memory locations, which allows for efficient indexing but can make insertions and deletions costly. A linked list, on the other hand, consists of nodes that are not stored in a contiguous memory location; each node points to the next node. This allows for efficient insertions and deletions but slower access time, as elements cannot be directly indexed.
Question: What is a stack, and where is it used?
Answer: A stack is a linear data structure that follows the Last In, First Out (LIFO) principle, meaning the last element added to the stack will be the first to be removed. Stacks are used in numerous applications like function call management in programming languages, undo mechanisms in text editors, and for evaluating expressions and syntax parsing.
Question: Describe a queue and its types.
Answer: A queue is a linear data structure that follows the First In, First Out (FIFO) principle, where the first element added is the first to be removed. Queues are used in scenarios like managing requests on a single shared resource (like a printer), handling asynchronous data (like in web servers), and for breadth-first search in algorithms. Types of queues include the simple queue, circular queue, priority queue, and double-ended queue (deque).
Question: What is a hash table, and how does it work?
Answer: A hash table is a data structure that implements an associative array, a structure that can map keys to values. A hash function is used to compute an index into an array of slots, from which the desired value can be found. Ideally, the hash function will assign each key to a unique slot, but due to the size of the hash table, this is not always possible. Hash tables are known for their efficient search, insert, and delete operations.
Question: Explain binary trees and their applications.
Answer: A binary tree is a tree data structure in which each node has at most two children, referred to as the left child and the right child. It is used in numerous applications such as expression parsing, searching and sorting algorithms, and improving database indexing. Binary trees serve as the basis for more complex structures like balanced trees (AVL trees, red-black trees) and binary heaps.
SQL Interview Questions
Question: What is SQL?
Answer: SQL (Structured Query Language) is a programming language used to manage and manipulate relational databases. It allows users to query and update data, define and modify the structure of databases, and perform various operations like insertions, deletions, and updates on the data.
Question: What are the different types of SQL commands?
Answer: SQL commands are broadly categorized into four types:
- DDL (Data Definition Language): Used to define the database structure, such as CREATE, ALTER, and DROP.
- DML (Data Manipulation Language): Used to manipulate the data in the database, such as INSERT, UPDATE, and DELETE.
- DQL (Data Query Language): Used to retrieve data from the database, primarily SELECT.
- DCL (Data Control Language): Used to manage access permissions and security, such as GRANT, and REVOKE.
Question: Explain the difference between INNER JOIN and LEFT JOIN.
Answer:
- INNER JOIN: Returns rows when there is at least one match in both tables based on the join condition.
- LEFT JOIN: Returns all rows from the left table (first table mentioned) and the matched rows from the right table, with NULL values where there is no match.
Question: What is a subquery in SQL?
Answer: A subquery, also known as an inner query or nested query, is a query within another SQL query. It can be used to retrieve data that will be used by the main query or to filter results based on the results of the subquery.
Question: Explain the difference between UNION and UNION ALL.
Answer:
- UNION: Combines the results of two or more SELECT statements and removes duplicates.
- UNION ALL: Combines the results of two or more SELECT statements, including duplicates.
Question: How do you find the second-highest salary from an Employee table?
Answer:
SELECT MAX(salary) AS second_highest_salary FROM Employee
WHERE salary < (SELECT MAX(salary) FROM Employee);
Question: Write an SQL query to count the number of employees in each department.
Answer:
SELECT department, COUNT(employee_id) AS num_employees FROM Employees
GROUP BY department;
Question: Explain the ACID properties in SQL.
Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties ensure that database transactions are processed reliably:
- Atomicity: Ensures that all operations in a transaction are completed successfully, or none are.
- Consistency: Ensures that the database remains in a consistent state before and after the transaction.
- Isolation: Ensures that transactions are executed independently of each other, preventing interference.
- Durability: Ensures that once a transaction is committed, the changes are permanent and persistent, even in case of system failure.
Python Interview Questions
Question: Explain the difference between a list and a tuple in Python.
Answer:
List:
- Mutable (can be modified after creation).
- Created with square brackets [].
- Supports methods like append(), remove(), and pop().
Tuple:
- Immutable (cannot be modified after creation).
- Created with parentheses ().
- Used for fixed data that doesn’t change, supports methods like count() and index().
Question: What is the difference between Python 2 and Python 3?
Answer:
Python 2:
- Legacy version, no longer maintained since 2020.
- Print is a statement: print “Hello”
- Division of integers results in integer: 5 / 2 = 2
Python 3:
- Current and actively developed version.
- Print is a function: print(“Hello”)
- Division of integers results in float: 5 / 2 = 2.5
Question: What is the difference between __str__ and __repr__?
Answer:
__str__:
- Returns a string representation of the object.
- Intended for end-users for readability.
__repr__:
- Returns an unambiguous string representation of the object.
- Intended for developers for debugging.
Question: Explain the use of *args and **kwargs in Python.
Answer:
*args:
- Used to pass a variable number of non-keyworded arguments to a function.
- Arguments are captured as a tuple.
**kwargs:
- Used to pass a variable number of keyworded arguments to a function.
- Arguments are captured as a dictionary.
Conclusion
Preparing for a data science and analytics interview at Walt Disney Company requires not just knowledge of algorithms and techniques, but also a passion for creativity, innovation, and storytelling. Be ready to showcase your technical skills, problem-solving abilities, and how you can use data to create magical experiences for Disney’s audiences around the globe. Best of luck on your interview journey!
