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Data Science Interview Questions

Data Science Interview Questions for Freshers


Welcome to the world of data science, where the demand for skilled professionals is skyrocketing! As you embark on your journey to master the intricacies of this dynamic field, it’s crucial to prepare for the inevitable – the data science interview. Whether you’re a fresher eager to make your mark or a seasoned professional looking to upskill, acing the interview is the key to unlocking exciting opportunities.

In this blog, we’ll delve into some fundamental data science interview questions tailored for freshers.

1. What is Data Science?

Answer: Data Science is a multidisciplinary field that uses scientific methods, processes, algorithms, and systems to extract knowledge and insights from structured and unstructured data.

2. Differentiate Between Descriptive and Inferential Statistics.

Answer: Descriptive statistics, on the one hand, summarize and describe data, whereas inferential statistics, on the other hand, make inferences and predictions about a population based on a sample of data.

3. Explain the Concept of Feature Engineering.

Answer: Feature engineering involves creating new features or transforming existing ones to improve the performance of machine learning models.

4. What is the Difference Between Machine Learning and Deep Learning?

Answer: While machine learning is a broader concept that includes various techniques for making predictions, deep learning is a subset of machine learning that involves neural networks with multiple layers.

5. How Does K-Means Clustering Work?

Answer: K-means clustering partitions data into ‘k’ clusters based on similarity, to minimize the within-cluster sum of squares.

6. What is Overfitting, and How Can it be Prevented?

Answer: Overfitting occurs when a model performs well on training data but poorly on new data. Preventive measures against overfitting include regularization techniques, cross-validation, and using more data.

7. Explain the Bias-Variance Tradeoff.

Answer: The bias-variance tradeoff involves balancing a model’s ability to capture underlying patterns in data (low bias) with its sensitivity to noise (low variance).

8. What is Cross-Validation?

Answer: Cross-validation is a technique used to assess the performance of a model by splitting the data into multiple subsets, training on some, and testing on others.

9. How Does Logistic Regression Work?

Answer: Logistic regression, a binary classification algorithm, models the probability of an event occurring using the logistic function.

10. What is the ROC Curve?

Answer: The Receiver Operating Characteristic (ROC) curve represents the trade-off between true positive rate and false positive rate for different thresholds of a binary classification model.

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11. Explain the Difference Between Supervised and Unsupervised Learning.

Answer: Supervised learning involves training a model on labeled data, while unsupervised learning deals with unlabeled data to find hidden patterns.

12. What is A/B Testing?

Answer: A/B testing is a statistical method used to compare two versions of a product or process to determine which performs better.

13. How Does Random Forest Work?

Answer: Random Forest, an ensemble learning method, constructs multiple decision trees during training and outputs the mode of the classes for classification tasks.

14. What is a Confusion Matrix?

Answer: A confusion matrix is a table describing the performance of a classification model, showing true positives, true negatives, false positives, and false negatives.

15. Explain Principal Component Analysis (PCA).

Answer: PCA is a dimensionality reduction technique transforming high-dimensional data into a lower-dimensional space while preserving the most important information.

16. What is Gradient Descent?

Answer: Gradient Descent, an optimization algorithm, minimizes the cost function of a model by iteratively adjusting its parameters.

17. How Do You Handle Missing Data?

Answer: Missing data can be managed through imputation, deletion, or advanced techniques like predictive modeling to fill in the gaps.

18. Define Normal Distribution.

Answer: Normal distribution, a symmetric, bell-shaped probability distribution, sees the majority of data points clustering around the mean.

19. What is the Curse of Dimensionality?

Answer: The curse of dimensionality pertains to the challenges and sparsity arising when working with high-dimensional data, making analysis and modeling more difficult.

20. Why is Python Preferred for Data Science?

Answer: Python is favored for data science due to its simplicity, extensive libraries (such as NumPy, Pandas, and Scikit-learn), and vibrant data science community.

21. Differentiate between univariate, bivariate, and multivariate analysis.

Univariate Analysis:

Univariate analysis involves examining a single variable in isolation. Its purpose is to describe the characteristics and distribution of that specific variable. For instance, consider a dataset containing the ages of a group of individuals. Univariate analysis of this dataset would involve calculating measures such as the mean, median, and mode of age. A histogram or a box plot could be used to represent the distribution of ages visually.


Suppose you have a dataset of the heights of students in a class. Univariate analysis would focus on understanding the distribution of heights, calculating measures like the average height, and creating visualizations like a histogram to show the frequency of different height ranges.

Bivariate Analysis:

Bivariate analysis involves studying the relationship between two variables. The objective is to explore how changes in one variable relate to changes in another. Taking the example of the student dataset, bivariate analysis could be used to examine if there’s a correlation between the students’ heights and their weights. A scatter plot would be a common visualization tool for bivariate analysis.


Consider a dataset containing both the hours of study and the exam scores of students. Bivariate analysis in this case would explore whether there’s a correlation between the hours of study and the exam scores, using techniques like scatter plots or calculating correlation coefficients.

Multivariate Analysis:

Multivariate analysis extends the analysis to three or more variables simultaneously. It aims to understand the complex relationships and interactions among multiple variables. Continuing with our student dataset, multivariate analysis might involve considering not just height and weight, but also factors such as study hours, sleep patterns, and nutrition. This approach aims to provide a more comprehensive understanding of academic performance.


In a marketing context, suppose you want to analyze the sales of a product. Multivariate analysis might entail the simultaneous consideration of variables such as advertising expenditure, seasonality, and competitor pricing. Additionally, this analysis could encompass other factors to provide a comprehensive understanding of the situation. Techniques like regression analysis might be employed to model how these factors collectively influence sales.

Are you a fresher? Delve into our comprehensive blog on ‘How to Start a Career in Data Science‘ for invaluable insights and guidance.”

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