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What are the commonly asked data scientist interview questions?

Data Science

Blog Date
December 20,

In the contemporary professional landscape, data science emerges as an exceptionally sought-after career path, primarily owing to its pivotal role in driving informed decision-making across diverse sectors. The burgeoning demand for data scientists has elevated competition, making interviews rigorous assessments of a candidate’s analytical prowess. The field’s appeal is underscored by its financial rewards, with professionals commanding substantial remuneration. Amidst this competitive environment, job opportunities in data science are abundant, reflecting the increasing reliance on data-driven insights. 

Aspiring data scientists should be well-prepared to navigate a diverse array of questions that span technical expertise, analytical thinking, and practical application of knowledge. This post explores frequently asked questions in data scientist interviews, offering insights into key areas candidates should focus on during their preparation.

Read more: Grow your career with a master’s in data science 

Top 25 data science interview questions and how to answer them

Let us delve into the common interview queries for data scientist roles, along with suitable responses for each of them. 

  1. What is data science, and how does it differ from traditional analytics?

The interdisciplinary area of data science employs scientific procedures, systems, algorithms, and methodologies to glean insights and knowledge from both structured and unstructured data. In contrast to conventional analytics, data science uses sophisticated methods like machine learning to forecast future patterns and behaviors, going beyond descriptive statistics.

  1. Explain the steps of the data science lifecycle.

The data science lifecycle encompasses several stages. The problem is first defined, then data is gathered and cleaned, and an exploratory data analysis is conducted to gain an understanding of the dataset. Feature engineering involves creating relevant features, and then models are built, evaluated, and fine-tuned. The final stages include deploying the model into production and maintaining its performance over time.

  1. What distinguishes supervised learning from unsupervised learning?

In supervised learning, a model is trained with a labeled dataset and input-output pairs teach the algorithm. In contrast, unsupervised learning deals with unlabelled data, aiming to identify patterns, relationships, or structures within the data without explicit guidance.

  1. Describe the curse of dimensionality.

The curse of dimensionality refers to challenges that arise when dealing with high-dimensional data. As the number of features increases, the data becomes sparse, making it difficult to generalize patterns. This can lead to increased computational complexity and issues like overfitting when modeling.

  1. Explain the concept of regularization.

Overfitting in machine learning models is avoided with the use of regularization. It entails penalizing large coefficients in the model’s cost function, thereby minimizing excessively complicated models. L1 and L2 regularization are two regularization techniques that can enhance a model’s generalization capabilities.

  1. What is cross-validation, and why is it important?

Cross-validation is a validation technique used to assess a model’s performance by partitioning the dataset into multiple subsets. A more robust evaluation of the model’s generalization performance is possible since it is trained on several combinations of these subsets.  It helps identify potential issues like overfitting and ensures the model’s reliability on new, unseen data.

  1. Differentiate between precision and recall.

Precision measures the accuracy of positive predictions, indicating the ratio of true positive predictions to the total predicted positives. Recall, on the other hand, gauges the model’s ability to capture all relevant instances and is the ratio of true positive predictions to the actual positives. These metrics are often in the trade-off, and the balance depends on the specific goals of the model.

  1. What is the purpose of feature engineering?

Feature engineering involves transforming raw data into a format that enhances a model’s performance. This includes creating new features, handling missing values, scaling, and other techniques to provide the model with the most relevant and discriminative information for making accurate predictions.

  1. Explain the concept of A/B testing.

A statistical technique called A/B testing is applied in experimentation for comparing two versions (A and B) of a variable. It is commonly employed in assessing changes to websites, applications, or marketing strategies. By randomly assigning users to different versions and analyzing the results, A/B testing helps determine the most effective approach based on measurable outcomes.

Check out: Concepts to learn in MBA analytics and data science 

  1. What is the difference between bagging and boosting?

Training several instances of the same model on various subsets of the data and averaging the predictions is known as bagging (Bootstrap Aggregating). Boosting, on the other hand, focuses on sequentially training models, with each subsequent model giving more weight to misclassified instances. Both techniques aim to improve the model’s overall performance and robustness.

  1. Discuss the bias-variance trade-off.

The bias-variance trade-off is very important in model development. When a real-world problem is oversimplified and results in underfitting, this is known as bias. Variance, on the other hand, is the error introduced by modeling the noise in the training data, causing overfitting. The trade-off involves finding the right balance to minimize both bias and variance, ultimately optimizing the model’s predictive performance on new, unseen data.

  1. Explain the term “p-value” in statistics.

A statistical metric called the p-value is used to assess how significant a hypothesis test’s findings are. It represents the probability of observing results as extreme as the ones obtained, assuming the null hypothesis is true. An alternative hypothesis is frequently accepted in place of the null hypothesis when a lower p-value indicates greater evidence against the null hypothesis.

  1. What is the purpose of the ROC curve?

The Receiver Operating Characteristic (ROC) curve is a graphical representation used to assess the performance of a binary classification model across different decision thresholds. It demonstrates the trade-off between the false positive rate (1-specificity) and the actual positive rate (sensitivity).  The model’s capacity for discrimination is summarized by the area under the ROC curve (AUC).

  1. Describe the difference between L1 and L2 regularization.

L1 regularization adds the absolute values of coefficients to the model’s cost function, promoting sparsity by driving some coefficients to exactly zero. L2 regularization adds the squared values of coefficients, penalizing large coefficients and encouraging a more distributed impact. L1 regularization is useful for feature selection, while L2 regularization helps prevent overfitting.

  1. What is the purpose of a confusion matrix?

An extensive study of a model’s performance in binary or multiclass classification can be found in a table called a confusion matrix. It includes metrics such as true positives (correctly predicted positive instances), true negatives (correctly predicted negative instances), false positives (incorrectly predicted positive instances), and false negatives (incorrectly predicted negative instances). From these, various metrics like precision, recall, and F1 score can be derived.

  1. Describe the concept behind recommendation systems’ collaborative filtering.

Recommendation systems employ the collaborative filtering process to offer users personalized choices. The underlying premise of this approach is that customers with comparable prior choices are likely to have similar future preferences. By utilizing trends in user activity, collaborative filtering—which can be person- or item-based and help locate related individuals or items—improves referral accuracy.

  1. How does a decision tree work, and what are its advantages and disadvantages?

A decision tree is a model that resembles a tree and is used to make judgements based on input feature values. It splits the data recursively into subsets, with each split determined by the most informative feature. Advantages include interpretability, ease of visualization, and handling of non-linear relationships. Disadvantages involve sensitivity to noisy data, potential overfitting, and instability with small changes in the data.

  1. What is the significance of the term “p-hacking”?

P-hacking refers to the practice of manipulating or cherry-picking data and statistical analyses to achieve a statistically significant result. This can lead to false or misleading conclusions, as the significance level is inflated. To maintain the integrity of statistical analyses, it is essential to predefine hypotheses, conduct analyses transparently, and be cautious of selective reporting.

  1. Discuss the concept of feature importance.

Feature importance measures the contribution of each feature to a model’s predictive performance. It helps identify which features have the most significant impact on predictions. Techniques like permutation importance, tree-based methods, and linear model coefficients can be used to assess feature importance. Understanding feature importance aids in feature selection, model interpretation, and focusing efforts on key variables.

  1. What is the purpose of cross-entropy loss in classification problems?

Cross-entropy loss, or log loss, is a measure used in classification problems to quantify the difference between predicted and actual probability distributions. It penalizes models more heavily for confidently incorrect predictions and encourages accurate estimation of class probabilities. Cross-entropy loss is commonly used in logistic regression and neural networks for classification tasks.

  1. Explain the terms precision, recall, and F1 score.

Precision is the ratio of correctly predicted positive observations to the total predicted positives, highlighting the model’s accuracy in positive predictions. Recall is the ratio of correctly predicted positive observations to the actual positives, emphasizing the model’s ability to capture all relevant instances. The F1 score is a balanced metric that takes into account both false positives and false negatives. It is calculated as the harmonic mean of precision and recall.

  1. What is the difference between a random forest and a gradient-boosting machine?

Random forests build multiple decision trees independently and combine their predictions through averaging or voting. They focus on reducing variance and improving robustness. Gradient boosting builds trees sequentially, with each tree correcting the errors of the previous ones. It emphasizes reducing bias and often achieves higher predictive accuracy, but it may be more prone to overfitting.

  1. How do you handle missing data in a dataset?

Handling missing data involves strategies such as imputation (filling missing values with estimated ones), removal of missing values, or advanced methods like predictive modeling to impute missing values based on other features. The choice of method depends on the nature of the data and the impact of missing values on the analysis.

  1. Discuss the concept of deep learning.

Deep learning involves training neural networks with multiple layers (deep neural networks) to automatically learn hierarchical representations of data. It performs exceptionally well in applications like complicated pattern recognition, natural language processing, and picture and speech recognition. Deep learning designs allow complex characteristics to be automatically extracted from raw data, such as Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs).

  1. In data science, what distinguishes deductive from inductive reasoning?

Inductive reasoning involves deriving general principles or patterns from specific observations or data. This is frequently used in data science about model construction and prediction based on observable patterns. Conversely, deductive reasoning begins with basic principles or hypotheses and applies them to particular situations. It is commonly used in hypothesis testing and model validation, applying known principles to assess specific instances or predictions.

Check out: Importance of analytics and data science for managers 

Online data science courses: The ideal way to advance your knowledge and skills

Online data science courses represent an ideal pathway for advancing one’s knowledge and skills in this dynamic field. These courses offer a flexible and accessible learning environment, allowing professionals to balance their studies with work commitments. Renowned platforms provide curated content developed by industry experts, ensuring relevance and applicability. The diverse range of topics covered, from machine learning to statistical analysis, caters to different facets of data science, creating a comprehensive learning experience. Moreover, participants benefit from hands-on projects and real-world applications, translating theoretical concepts into practical expertise. 

The interactive nature of online courses fosters a collaborative learning community, enabling networking opportunities with peers and mentors. As the demand for data-driven insights continues to rise across industries, engaging in online data science courses equips individuals with the expertise needed to navigate the evolving landscape, making it an ideal avenue for professional development.

Also read: Leveraging analytics and data science for non-tech professionals 

Online Manipal: Your #1 choice for exceptional online data science courses

Online Manipal stands as the unparalleled choice for individuals seeking top-tier data science education, exemplified by the Online MBA in Data Science from MAHE and the Online MBA in Analytics and Data Science from Manipal University Jaipur. These programs boast a distinctive blend of theoretical rigor and practical application, equipping learners with a profound understanding of data science essentials. Highlights encompass a meticulously designed curriculum aligned with industry demands, hands-on projects to enhance real-world skills, and an esteemed faculty renowned for its scholarly achievements. The flexibility of online learning ensures accessibility without compromising the quality of education, making Online Manipal the definitive destination for those aiming to excel in the dynamic field of data science.

Read More: MBA Analytics & Data Science course syllabus


In conclusion, acing a data science interview demands a comprehensive approach that encompasses technical proficiency, problem-solving acumen, effective communication, ethical considerations, and a commitment to continuous learning. Consider the aforementioned data scientist interview question examples to get interview-ready. By preparing for commonly asked questions in data scientist interviews, candidates can not only navigate the intricacies of the interview process but also position themselves as indispensable assets in the competitive arena of data science opportunities. 

To take your expertise to new heights, consider enrolling in an Online MBA in Data Science from MAHE or an Online MBA in Analytics and Data Science from Manipal University Jaipur. These prestigious programs provide you with a transforming edge for a successful professional path in the ever-evolving field of data science by offering a thoughtful fusion of academic rigor and practical insights.


Information related to companies and external organizations is based on secondary research or the opinion of individual authors and must not be interpreted as the official information shared by the concerned organization.

Additionally, information like fee, eligibility, scholarships, finance options etc. on offerings and programs listed on Online Manipal may change as per the discretion of respective universities so please refer to the respective program page for latest information. Any information provided in blogs is not binding and cannot be taken as final.

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