Machine Learning Interview Questions

You’ll need to pass a comprehensive and challenging interview process if you want to secure a place in data science. An interview for Machine Learning demands a detailed interview process in which applicants are tested on different levels, such as technical and programming abilities, understanding of methodology, and knowledge of dominant theories. When you intend to seek employment in machine learning, it is important to know what sort of interview questions recruiters and hiring managers can usually ask.

In large product-based corporations and start-ups, this is an effort to help you crack the machine learning interviews. Machine learning interviews at large companies typically require a thorough understanding of data structures and algorithms. You’ll be tested for a variety of abilities during the process, including:

  • Your expertise in technical and programming work
  • Your capacity to construct solutions to challenges with open ends
  • Your ability to reliably implement machine learning
  • Your ability to evaluate information with a range of techniques
  • Your expertise in communication, cultural fit, etc.
  • And your mastery of key data science and machine learning concepts

In this article, we have presented some samples of questions and answers from machine learning interviews to give you a deep insight into questions for a machine learning interview.

1. How do you define Machine learning?

Ans. A class of Artificial Intelligence is Machine Learning. Algorithms that interpret data, learn from that data, and then apply what they have learned to make better decisions, is all about machine learning. It functions with particular areas only.

For example, if we create a machine learning model to identify dog images, it will only deliver results for dog images, but if we have new data such as cat images, it will become inactive. Machine learning is used in different ways such as online recommendation systems, Google search algorithms, email spam filtering, Facebook auto friend tagging, etc.

2. What are the different types of Machine Learning?

Ans. Three categories of machine learning exist:

Supervised Learning

A model makes predictions or judgments in supervised machine learning given past or labeled evidence. Labeled data refers to data sets that are given and thus made more valuable by tags or labels.

Unsupervised Learning

We don’t have labeled data in unsupervised learning. In the input data, a model can recognize patterns, anomalies, and relationships.

Learning Reinforcement

The model will learn based on the incentives it obtained for its previous behavior, using reinforcement learning.

3. What is the difference between Artificial Intelligence and Machine Learning?

Ans. AI is a broader term for the development of intelligent machines that can mimic the capability and actions of human reasoning, while machine learning is an algorithm or subset of AI that enables machines to learn from data without being specifically programmed. Rather than using algorithms that can run on their intelligence, the Artificial Intelligence System would not require pre-programming. Machine learning operates under an algorithm that uses historical data to learn on its own. It functions with particular areas only.

4. What is the difference between Machine Learning and Deep Learning?

Ans. Machine learning allows computers, based on historical results, to take decisions on their own. For learning, it only takes a small amount of data. The low-end system works well because you don’t need big machines. The problem is broken into two pieces and separately solved and then merged.
With the assistance of artificial neural networks, Deep Learning helps computers to make decisions. It takes a significant amount of data for training. As it takes a lot of processing resources, it needs high-end computers. In an end-to-end way, the issue is solved.

5. How will you differentiate between Clustering and Classification?

Ans. Two methods of pattern recognition used in machine learning are classification and clustering. Although there are some parallels between the two methods, the distinction lies in the fact that predefined classes are used in classification in which objects are assigned, while clustering recognizes similarities between objects, grouping them according to common characteristics and separating them from other categories of objects.

6. State the difference between classification and Regression

Ans. Classification is used to obtain discrete outcomes, classification is used to sort data into certain groups, such as classifying e-mails into categories of spam and non-spam.

In comparison, when dealing with continuous statistics, we use regression analysis, such as forecasting stock markets at a certain point in time.

7. How will you select a Machine Learning model/algorithm for a given data set?

Ans. The machine learning algorithm to be used relies entirely on the form of data in the dataset in question. And if the input is continuous, we use linear regression. The bagging algorithm would do well if data shows non-linearity then. If the data for certain business purposes need to be analyzed/interpreted, then we can use decision trees or SVM. If the dataset consists of images, videos, audio, then it will be useful for neural networks to get the solution correctly.

So, for a given scenario or a data set, there is no certain metric to determine which algorithm to use. Using EDA, we need to analyze the information and understand the goal to use the dataset to come up with the right fit algorithm. It is essential to analyze all the algorithms in depth.

8. Differentiate between covariance and correlation.

Ans. Covariance tests how two variables are compared to each other and how one differs in response to the other variable’s shifts. If the value is positive, it means that there is a clear relationship between the variables and, provided that all other parameters remain unchanged, one will increase or decrease with an increase or decrease in the base variable.
The relationship between two random variables is quantified by correlation and has only three distinct values, i.e., 1, 0, and -1.
1 indicates a positive relationship, -1 indicates a negative relationship, and 0 reflects the independence of each other from the two variables.

9. Differentiate between causality and correlation.

Ans. Causality extends to cases where one action, such as X, generates an outcome, such as Y, while correlation only connects one action (X) to another action(Y), but X does not necessarily cause Y.

10. Define Bias and Variance.

Ans. When the expected values are farther away from the real values, the bias in a machine learning model appears. A model where the projection values are very similar to the real ones is demonstrated by low bias.

Variance refers to the extent that when trained with various training data, the goal model would change. The variance should be minimized for a good model.

11. What are the three stages to build models in machine learning?

Ans. The three steps of the development of a model for machine learning are:

Building Model

Select an effective model algorithm and train it according to the specifications.

Testing Model

Check the model’s accuracy through the test results.

Application of Model

Using the final model for real-time projects to make the requisite improvements after checking.

12. What is overfitting in Machine Learning?

Ans. Overfitting is defined as a modeling error that arises when a specific function corresponds very closely to a certain set of data. As a result, overfitting may unable to accommodate additional data which affects the accuracy of future prediction. The validation matrices like accuracy and loss help us in identifying the overfitting. Normally, these validation metrics increase up to a certain level and start declining when affected by the overfitting. The overfitting problem can be avoided by taking these stepst

Training with more data

Training the model with more data is the simplest technique for preventing overfitting. This method helps the algorithm in better detection of signals to reduce the number of errors.

Data Augmentation

In the data augmentation technique, the sample data appear different each time it is processed by the model. This process makes the data set unique and successfully avoids the model to learn about the characteristics of the datasets.

Data simplification

Overfitting can also appear due to the complication in the model and the large volume of the dataset. The data simplification process is utilized to decrease the complexity of the data set and model.


In the Ensembling technique, two or more prediction outcomes from different models combine to effectively counter the overfitting problem.

13. Explain the term “kernel trick”.

Ans. When there are a variety of dimensions in the space, it is very difficult to effectively compute all the data from different dimensions. In this scenario, the kernel trick allows us to work in the basic feature space without any computation about the data coordinates in the higher dimensional space. It is a very accurate, reliable, and less expensive method to effectively modify the data into a higher dimension. The application aspect of the kernel is not limited to the Support Vector Machines (SVM) algorithm but can also be utilized for any computational function demand dot product.

14. How well do you understand the confusion matrix? Why is it employed in ML?

Ans. An N×N matrix that is utilized for assessing the performance of the classification model is generally known as the confusion matrix. Here the N specifies the number of target classes. The confusion matrix compares the predicted values from the machine learning model with the actual values. This comparison grants a holistic view to know about the performance of the employed classification model and what kind of errors it is creating along with its effects on the outcomes.

15. What is the difference between a discriminative model and a generative model?

Ans. In Machine learning, different models are broadly classified into two basic categories: Generative and Discriminative Model.

Generative Models

The main objective of generative models is to distribute the individual classes in the specific dataset. These models effectively utilize the theory of joint probability where the stated input feature and required output co-exist at the same time. They use likelihood and probability to organize the dataset and differentiate between various kinds of class labels in the specified dataset. These models can generate the instance of new datasets. The presence of outliers is the major drawback of generative models. Some of the most prominent examples of generative models are Naïve Bayes (generally known as Bayesian Networks), Hidden Markov Model, and Linear Discriminant Analysis (LDA).

Discrimination Models

The models which tend to learn about the boundary layer between the labels and the classes in the data set are generally termed as discrimination or conditional models. The main purpose of these models is to discover the decision boundary that efficiently separates the different classes from each other. The discrimination model separates these classes based on conditional probability without making any assumptions in the given dataset. These models are considered to be more robust against outlier as compared to the generative models. Some prominent discrimination models used in machine learning are Logistic Regression, Support Vector Machine, Decision Tree, and Random Forest.

16. What is your understanding of neural networks?

Ans. The neural network is an important class of machine learning algorithms. These models are utilized for modeling the complex patterns in the given dataset with the help of non-linear activation functions and multiple hidden layers.

The neural networks get the input and pass it through a variety of hidden layers or you can say mini functions. The output shows the prediction by combining inputs from all the neurons. Several techniques like gradient descent are being used for iterative training of different neural networks.

After each training cycle, the deviation error matrix is calculated and propagated back through networks with the help of the backpropagation technique. Each of the neuron’s coefficients is generally termed as weights then modified according to their contribution to the total error. This process continues until the overall network error drops below the threshold level.

17. What is the pruning of decision trees?

Ans. In machine learning, the pruning technique is used for reducing the size of the decision trees by detaching different parts of the tree that have a minimum or zero contribution towards the classification of instances. At each instance, we first check the cross-validation error before splitting the tree.

18. What is Regularization in ML and why do we employ it?

Ans. In machine learning, the regularization technique is used to calibrate the coefficients of various multi-linear regression models for decreasing the value of the loss function. As the linear regression model consists of a variety of features, it suffers from several problems such as:

Overfitting: The model fails in generalizing on unseen data

Computationally Intensive: The model becomes very intensive due to huge data computation

Multicollinearity: The model suffers from the effect of Multicollinearity

The regularization technique helps us in overcoming all the above state problems in machine learning.

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