Top 20 Data Science Interview Questions & Answers - 2023 Edition

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Sameer SM

Into The Realms Of Data Science
Into The Realms Of Data Science


Data science plays a pivotal role in today's data-driven world, enabling organizations to make informed decisions by extracting insights from vast datasets. To ensure they hire the best data scientists, recruiters must ask the right questions during interviews.

In this blog, we'll explore the essential aspects of data science, the interview process, and provide answers to the top 20 data science interview questions for 2023.

Understanding Data Science

Data science is a multidisciplinary field that employs scientific methods, algorithms, and systems to extract knowledge and insights from large volumes of data. It empowers organizations to analyze data from diverse sources, uncover patterns, trends, correlations, and make data-driven decisions.

Responsibilities of Data Scientists

Data scientists utilize various techniques, including machine learning, deep learning, natural language processing, predictive analytics, and data visualization, to analyze extensive datasets. They are also tasked with developing models to forecast future events or trends, providing valuable insights into business operations and customer behavior.

The Lifecycle of Data Science

Data science follows a well-defined lifecycle:

  • Data Acquisition
  • Data Wrangling
  • Exploratory Data Analysis
  • Modeling & Inference
  • Deployment

Each step builds upon the previous one, ensuring a systematic approach to extracting meaningful insights from data.

Data Science vs. Data Analytics

Data science and data analytics are related fields but differ in focus. Data science delves into complex patterns within large datasets, while data analytics interprets existing data to generate insights. Both require programming skills, such as Python and R, but data scientists have a broader skill set for handling intricate data patterns.

Conducting a Data Science Interview

Conducting a data science interview requires precision to evaluate candidates' knowledge, problem-solving abilities, and critical thinking.

Here are four essential steps for recruiters:

  1. Reevaluate Your Hiring Process: Employ hiring platforms or tools like Codejudge to accurately assess data science skills. Ensure your process aligns with the specific requirements of data science roles.
  2. Assess Understanding of Business Problems: Evaluate candidates' ability to observe and analyze business data that influences decision-making. Successful data scientists must connect data insights to real-world applications.
  3. Evaluate Thought Process: Focus on practical responses to real-life business problems and specific projects rather than generic data science concepts. Analyze candidates' logic in selecting algorithms or techniques for specific datasets.
  4. Emphasize Thought Process: Prioritize candidates' thought processes over their ability to use specific tools or programming languages. The ability to reason through complex problems is crucial in data science roles.

Top 20 Data Science Interview Questions & Answers (2023)

1) Sampling Techniques: Explain common sampling techniques used in data analysis and their advantages.

  • Explanation: Common sampling techniques include random sampling, stratified sampling, and systematic sampling. Random sampling ensures each element has an equal chance of being chosen. Stratified sampling divides the population into subgroups, and samples are taken from each. Systematic sampling selects every nth item after a random start.
  • Advantages: Random sampling provides unbiased representation, stratified sampling ensures representation from all subgroups, and systematic sampling is straightforward and efficient.

2) Overfitting and Underfitting: Define overfitting and underfitting and list the conditions for each.

  • Definition: Overfitting occurs when a model learns noise in the training data rather than the underlying pattern, resulting in poor generalization. Underfitting happens when a model is too simplistic to capture the underlying structure of the data.
  • Conditions: Overfitting may occur with complex models or insufficient data, while underfitting is more likely with overly simple models.

3) P-Values: What do high and low p-values indicate in statistical analysis?

Indication: In statistical analysis, a high p-value suggests weak evidence against the null hypothesis, while a low p-value indicates strong evidence. Typically, p-values below 0.05 are considered statistically significant.

4) Survivorship Bias: Explain survivorship bias and its implications.

  • Explanation: Survivorship bias occurs when only surviving or successful subjects are considered in analysis, leading to skewed conclusions. It neglects the influence of factors that may have affected non-survivors.
  • Implications: It can result in overestimating success rates or underestimating risks.

5) Confounding Variables: Define confounding variables and their role in data analysis.

  • Definition: Confounding variables are additional factors that may influence the observed relationship between the independent and dependent variables in a study.
  • Role: They can lead to spurious correlations or misinterpretations if not controlled for in the analysis.

6) Types of Data Analysis: Differentiate between univariate, bivariate, and multivariate analysis.


  • Univariate analysis deals with a single variable.
  • Bivariate analysis explores relationships between two variables.
  • Multivariate analysis involves multiple variables simultaneously.

7) Dimensionality Reduction: Define dimensionality reduction and its benefits.

  • Definition: Dimensionality reduction involves reducing the number of variables in a dataset while preserving its essential features.
  • Benefits: It helps overcome the curse of dimensionality, improves model efficiency, and reduces computational complexity.

8) Eigenvectors and Eigenvalues: Explain what eigenvectors and eigenvalues are in linear algebra.

Explanation: In linear algebra, eigenvectors are vectors that remain unchanged in direction when a linear transformation is applied, and eigenvalues represent the scalar by which the eigenvector is scaled.

9) Logistic Regression: What is logistic regression, and when is it used?

  • Definition: Logistic regression is used for binary classification problems, predicting the probability of an event occurring.
  • Application: It is employed when the dependent variable is categorical with two possible outcomes.

10) Linear Regression: Define linear regression and its applications.

  • Definition: Linear regression models the relationship between a dependent variable and one or more independent variables with a linear equation.
  • Applications: Used for predicting numerical outcomes.

11) Deep Learning vs. Machine Learning: Explain the difference between deep learning and machine learning.

Difference: Machine learning involves algorithms that improve performance over time without explicit programming. Deep learning, a subset of machine learning, utilizes neural networks with multiple layers to perform tasks.

12) Neural Network Fundamentals: Describe the fundamentals of neural networks.

Description: Neural networks consist of interconnected nodes, or neurons, organized in layers, including input, hidden, and output layers. They mimic the human brain's structure to learn and make predictions.

13) Computational Graph: What is a computational graph, and how is it used in deep learning?

Definition: A computational graph visually represents mathematical computations in deep learning. Nodes represent operations, and edges represent data flow.

14) Auto-Encoders: Define auto-encoders and their role in neural networks.

Definition: Auto-encoders are neural network architectures used for unsupervised learning. They encode input data into a compressed representation and reconstruct the original data.

15) Correlation vs. Covariance: Differentiate between correlation and covariance.

Differentiation: Correlation measures the strength and direction of a linear relationship between two variables, while covariance measures their joint variability.

16) Algorithm Updates: How often should machine learning algorithms be updated?

Frequency: The frequency of updates depends on the nature of the data and the problem. In dynamic environments, frequent updates may be necessary to adapt to changes.

17) Supervised vs. Unsupervised Learning: Explain the differences between supervised and unsupervised learning.

Explanation: Supervised learning involves training a model using labeled data, while unsupervised learning deals with unlabeled data, discovering patterns without predefined outcomes.

18) Selection Bias: Define selection bias and why it's important to address it in research.

  • Definition: Selection bias occurs when the sample used in a study is not representative of the population, leading to skewed results.
  • Importance: Addressing it ensures that study findings are applicable and accurate for the entire population.

19) Data Cleaning: Why is data cleaning crucial in data analysis?

Cruciality: Data cleaning is crucial to eliminate errors, inconsistencies, and inaccuracies in datasets, ensuring the reliability of analyses and models.

20) Imbalanced Data: What is imbalanced data, and how can it be corrected in machine learning?

  • Definition: Imbalanced data refers to a situation where the distribution of classes is uneven, potentially leading to biased model performance.
  • Correction: Techniques like oversampling, undersampling, or using specialized algorithms can address imbalanced data.


Data science is a dynamic field, and interviews for data science positions require in-depth knowledge. Preparing for these interviews involves understanding key concepts and being able to answer questions like the ones listed above.

Whether you're a candidate or a recruiter, a strong grasp of data science fundamentals and the ability to reason through complex problems are essential for success in this exciting and rapidly evolving field.

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