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50+ Machine Learning Interview Questions And Answers

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14 January, 2022

A rigorous interview procedure is required for a Machine Learning interview, in which candidates are judged on numerous criteria such as technical and programming skills, method understanding, and clarity of basic concepts. If you want to apply for machine learning positions, you should be aware of the types of Machine Learning interview questions that recruiters and hiring managers are likely to ask.

We've put together a list of the most common top machine learning interview questions that you might encounter during your interview. 

  1. What is the difference between Artificial Intelligence (AI), Machine Learning (ML), and Deep Learning (DL)? 

The field of artificial intelligence (AI) is concerned with the creation of intelligent machines. Systems that can learn from experience (training data) are referred to as machine learning (ML), whereas systems that learn from experience on big data sets are referred to as deep learning (DL). AI can be thought of as a subset of machine learning. Deep Learning (DL) is similar to machine learning (ML), but it is more suitable for huge data sets. 

  1. What is the most significant distinction between supervised and unsupervised machine learning?

To train the model, the supervised learning technique requires labeled data. To solve a classification problem (a supervised learning task), for example, you'll need label data to train the model and labeled groups to categorize the data into. There is no need for a labeled dataset in unsupervised learning. This is the most significant distinction between supervised and unsupervised learning.

  1. When working with a data set, how do you choose important variables?

There are several methods for selecting key variables from a data set, including:

  • Before deciding on crucial factors, identify and eliminate linked variables.
  • The variables might be chosen using the 'p' values from Linear Regression Forward, Backward, and Stepwise selection methods.
  • Regression with a Lasso
  • Random Variable chart for the forest and plot
  • Top features can be chosen depending on the amount of information gained for the set of features offered.
  1. Explain the distinctions between causality and correlation.

Causality refers to circumstances in which one action, such as X, results in an outcome, such as Y, whereas correlation simply refers to the relationship between one action (X) and another action (Y), although X does not always result in Y.

  1. Almost every day, we take a look at machine learning software. What is the best way to apply machine learning to hardware?

To apply Machine Learning to hardware, we must first create ML algorithms in System Verilog, a Hardware Development Language, and then program them into an FPGA.

  1. In Machine Learning, when does regularisation come into play?

Regularization becomes important when the model begins to underfit or overfit. It's a type of regression that diverts or regularises the coefficient estimates toward zero. To minimize overfitting, it decreases flexibility and discourages learning in a model. The model's complexity decreases, and it improves its prediction ability.

  1. What is the relationship between standard deviation and variance?

The standard deviation measures how far your data deviates from the mean. The average degree to which each point differs from the mean, or the average of all data points, is called variance. Because Standard deviation is the square root of Variance, we can connect the two.

  1. Is a lot of variation in data a good thing or a negative thing?

Higher variance indicates that the data spread is wide and that the feature has a wide range of data. High volatility in a feature is usually regarded as a sign of poor quality.

  1. What would you do if your dataset has a high level of variance?

We could use the bagging technique to handle datasets with a lot of variation. With sampling replicated from random data, the bagging algorithm divides the data into subgroups. Random data is used to develop rules using a training algorithm after the data has been separated. The polling technique is then used to combine all of the model's projected results.

  1. Explain how the missing or corrupted values in the given dataset should be handled.

Dropping the corresponding rows or columns is a simple technique to deal with missing or corrupted values. We consider replacing missing or corrupted entries with new values if there are too many rows or columns to remove.

The IsNull() and dropna() functions in Pandas can be used to find missing values and drop rows or columns. Additionally, Pandas' Fillna() function substitutes erroneous values with placeholder values.

  1. What exactly is a time series?

A time series is a collection of numerical data points arranged in a logical order. It records the data points at regular intervals and follows the movement of the selected data points over a specified time period. There is no requirement for a minimum or maximum time input in a time series. Time series are frequently used by analysts to analyze data in order to meet their individual requirements.

  1. What is a Box-Cox transformation, and how does it work?

Because normality is the most common assumption made when applying various statistical techniques, the Box-Cox transformation transforms non-normal dependent variables into normal variables. When set to 0, the lambda argument indicates that this transform is comparable to log-transform. It is used to normalize the distribution and stabilize the variance.

  1. What's the difference between gradient descent (GD) and stochastic gradient descent (SGD)?

The algorithms Gradient Descent and Stochastic Gradient Descent determine the set of parameters that minimize a loss function.

Gradient Descend differs in that all training samples are assessed for each set of parameters. For the set of parameters identified in Stochastic Gradient Descent, just one training sample is examined.

  1. What is the backpropagation technique's exploding gradient problem?

The exploding gradient problem occurs when significant error gradients build and result in huge changes in neural network weights during training. Weight values can become so big that they overflow, resulting in NaN values. As with the vanishing gradient problem, this makes the model unstable and causes the learning process to stall.

  1. Can you list some of the benefits and drawbacks of decision trees?

Decision trees have the advantages of being easier to read, nonparametric, and thus resilient to outliers, and having a small number of parameters to tweak.

On the other hand, they have the problem of being prone to overfitting.

  1. What is a Fourier transform, and how does it work?

The Fourier Transform is a mathematical approach for converting any time function to a frequency function. Fourier transform and Fourier series are closely related concepts. It determines the overall cycle offset, rotation speed, and strength for all feasible cycles using any time-based pattern as input. Because it has functions of time and space, the Fourier transform is best applied to waveforms. When a waveform is subjected to the Fourier transform, it is decomposed into a sinusoid.

  1. What does it mean by marginalization? Describe the procedure.

Summing the probability of a random variable X given its combined probability distribution with other variables is known as marginalization. It's a case where the law of total probability is used.

P(X=x) = ∑YP(X=x,Y)

We may use marginalization to determine P(X=x, Y) given the joint probability P(X=x, Y). So, by exhausting cases on other random variables, one can identify the distribution of one random variable.

  1. When regression is conducted on different subsets of a given dataset, what could be the problem if the beta value for a given variable fluctuates way too much in each subset?

The fact that the beta values in each subgroup differ indicates that the dataset is diverse. To solve this issue, we can use a different model for each of the clustered subsets of the dataset, or we can use a non-parametric model like decision trees.

  1. What is the meaning of the term Variance Inflation Factor?

The Variation Inflation Factor (VIF) is the ratio of model variance to model variance when only one independent variable is present. The volume of multicollinearity in a set of multiple regression variables is estimated using VIF.

VIF = Model variance with one independent variable

  1. What is the name of the machine learning algorithm known as the lazy learner, and why is it so?

A sluggish learner, KNN is a Machine Learning algorithm. K-NN is a lazy learner since it does not learn any machine-learned values or variables from the training data, instead of calculating distance dynamically every time it wishes to classify and thereby memorize the training dataset.

  1. Is it possible to process images with KNN?

It is true that KNN can be used to process images. It is possible to do so by transforming the three-dimensional image into a single-dimensional vector and feeding it into KNN.

  1. What is the SVM algorithm's approach to self-learning?

This is taken care of by SVM's learning and expansion rates. The learning rate compensates or penalizes the hyperplanes for all of their incorrect moves, while the expansion rate is concerned with determining the maximum area of separation between classes.

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  1. In SVM, what are Kernels? List the most common kernels used in SVM, along with a scenario of how they're employed.

The kernel's job is to take data and turn it into the required format. RBF, Linear, Sigmoid, Polynomial, Hyperbolic, Laplace, and other prominent SVM Kernels include:

  1. In an SVM algorithm, what is a Kernel Trick?

Kernel Trick is a mathematical formula that can be used to discover the categorization zone between two classes when applied to data points. A classifier can be built based on the function chosen, whether linear or radial, which is solely dependent on the data distribution.

  1. What are ensemble models, and how do they work? Explain why ensemble techniques produce superior learning than typical categorization machine learning algorithms.

The ensemble is a collection of models that are used together for classification and regression prediction. Because it mixes numerous models, ensemble learning improves ML results. When compared to a single model, this provides for improved predictive performance.

They outperform individual models by reducing variance, averaging out biases, and reducing the risk of overfitting.

  1. What is an OOB error and how does it happen?

One-third of the data in each bootstrap sample was not used in the tree's construction, i.e. it was not included in the sample. Out of bag data is the name given to this type of information. Out-of-bag error is used to gain an unbiased evaluation of the model's accuracy over test data. Out of bag data is transmitted through each tree, and the outputs are averaged to determine the out-of-bag error. This percentage error is very effective at estimating the error in the testing set, and it doesn't require any further cross-validation.

  1. When compared to other ensemble methods, why is boosting a more stable algorithm?

Boosting concentrates on prior iteration faults until they are no longer relevant. In contrast, there is no corrective loop in bagging. This is why, in comparison to other ensemble algorithms, boosting is a more stable approach.

  1. How do you deal with data outliers?

An outlier is a data point that is significantly different from the rest of the data collection. Outliers can be found utilizing tools and functions such as box plots, scatter plots, Z-Scores, and IQR scores, and then handled based on the visualization we have. To deal with outliers, we can set a limit, employ modifications to reduce skewness in the data, and delete anomalies or errors if they are outliers.

  1. Make a list of the most widely used cross-validation procedures.

Cross-validation procedures are divided into six categories. The following are some of them:

  • K fold
  • Stratified k fold
  • Leave one out
  • Bootstrapping
  • Random search cv
  • Grid search cv
  1. Is there a way to test the likelihood of improving model correctness without using cross-validation techniques? If so, please elaborate.

Without using cross-validation approaches, it is possible to test for the likelihood of improving model correctness. We can achieve this by iterating the ML model for n iterations and recording the accuracy. Plot all of the accuracies and discard the 5% of values with a low likelihood. Take a measurement of the left [low] and right [high] cutoffs. We can say that the model can go as low or as high [as indicated within cut-off points] with the remaining 95% confidence.

  1. What is the significance of component rotation in Principle Component Analysis (PCA)?

Rotation is critical in PCA because it optimizes the separation within the variance acquired by all of the components, making component interpretation easier. We'll need extended components to represent component variance if the components aren't rotated.

  1. Why is logistic regression a classification method rather than a regression? What is the name of the function from which it is derived?

Given the categorical nature of the target column, linear regression is used to produce an odd function that is wrapped in a log function to use regression as a classifier. As a result, it is a classification approach rather than a regression. It comes from the cost function.

  1. When regression is conducted on different subsets of a given dataset, what could be the problem if the beta value for a given variable fluctuates way too much in each subset?

The fact that the beta values in each subgroup differ indicates that the dataset is diverse. To solve this issue, we can use a different model for each of the clustered subsets of the dataset, or we can use a non-parametric model like decision trees.

  1. Give an example of a well-known dimensionality reduction algorithm.

Principal Component Analysis and Factor Analysis are two popular dimensionality reduction approaches.

From a broader collection of measurable variables, Principal Component Analysis develops one or more index variables. A model for measuring a latent variable is factor analysis. This hidden variable is seen by the relationship it produces in a group of y variables and cannot be assessed with a single variable.

  1. How can we apply supervised learning algorithms with a dataset that lacks the goal variable?

Put the data into a clustering algorithm, find the best groupings, and label the cluster numbers as the new target variable. The dataset now contains both independent and target variables. This guarantees that the dataset is ready for supervised learning techniques.

  1. How do we address issues of sparsity in recommendation systems? How will we know if it's working? Explain.

The prediction matrix can be created using singular value decomposition. The root means square error (RMSE) is a metric that shows how near the prediction matrix is to the original matrix.

  1. Name and specify the approaches used in the recommendation system to find commonalities.

The techniques of Pearson correlation and Cosine correlation are utilized in recommendation systems to discover similarities.

  1. What does the term "instance-based learning" mean?

Instance-Based Learning is a set of regression and classification algorithms that create a class label prediction based on similarities to the training data set's nearest neighbors. These algorithms simply collect all of the data and provide an answer when requested. Simply said, they are a set of processes for solving new problems that are built on previous answers to problems that are comparable to the current challenge.

  1. What is the distinction between Lasso and Ridge?

Regularization techniques such as Lasso(L1) and Ridge(L2) penalize coefficients to find the best solution. The sum of the squares of the coefficients defines the punishment function in the ridge, while the sum of the absolute values of the coefficients is penalized in Lasso. ElasticNet is a hybrid penalizing function of both lasso and ridge that is used as a regularisation tool.

  1. How can you tell the difference between statistical modeling and machine learning?

Machine learning models are used to make accurate predictions about scenarios such as restaurant foot traffic, stock prices, and so on, whereas statistical models are used to infer associations between variables such as what drives restaurant sales: cuisine or ambiance.

  1. What do the terms Gamma and Regularization mean in SVM?

Influence is defined by gamma. Low numbers denote distance, whereas high values denote proximity. If gamma is too large, the radius of the support vectors' sphere of effect only comprises the support vector itself, and no amount of regularisation using C can prevent overfitting. If gamma is too small, the model is too limited to describe the data's complexity.

The regularisation parameter (lambda) is used to determine how important miss-classifications are. This can be used to illustrate the OverFitting tradeoff.

  1. Work to define the ROC curve

The ROC curve is a graphical representation of the difference between true positive and false-positive rates at various thresholds. It's utilized as a proxy for the true positives vs. false positives trade-off.

  1. What's the difference between a discriminative and generative model?

A generative model is one that learns diverse types of data. A discriminative model, on the other hand, will simply learn the differences between different types of data. When it comes to classification problems, discriminative models outperform generative models significantly.

  1. What is the difference between hyperparameters and parameters?

A parameter is an internal model variable whose value is estimated based on the training data. They're frequently saved as part of the model that's been taught. Weights, biases, and other variables are examples.

A hyperparameter is a variable that isn't part of the model and whose value can't be guessed from the data. Model parameters are frequently estimated using them. The selection of parameters is influenced by the implementation. Learning rate, buried layers, and so on are examples.

  1. Explain what a hash table is.

Hashing is a method of distinguishing unique objects from a bunch of similar items. In hashing algorithms, hash functions are huge keys that are turned into small keys. Hash function values are kept in hash tables, which are data structures.

  1. Explain the concepts of Eigenvectors and Eigenvalues.

When employing eigenvectors, linear transformations are useful. They are most commonly used in data science to create covariance and correlation matrices.

Simply expressed, eigenvectors are directional entities that can be used to apply linear transformation characteristics such as compression, flipping, and so on.

The magnitude of the linear transformation characteristics along each direction of an Eigenvector is measured in Eigenvalues.

  1. In a clustering algorithm, how would you define the number of clusters?

The silhouette score can be used to calculate the number of clusters. Using clustering techniques, we can often extract some conclusions from data in order to get a fuller picture of the number of classes represented by the data. In this example, the silhouette score assists us in determining the number of cluster centers along which we should cluster our data.

The elbow approach is another technique that can be used.

  1. What performance indicators may be used to estimate a linear regression model's effectiveness?

In this situation, the performance metric is as follows:

The Mean Squared Error (MSE) is a measure of how accurate

  • R2 rating
  • R2 score (adjusted)
  • Absolute mean score
  1. In decision trees, what is the default technique of splitting?

The Gini Index is the standard approach for partitioning decision trees. The Gini Index is a measurement of a node's impurity.

This can be altered by altering the classifier's parameters.

  1. What is the purpose of the p-value?

The p-value indicates the likelihood that the null hypothesis is correct. It tells us how statistically significant our findings are. In other words, the p-value determines a model's confidence in a specific result.

  1. Is it possible to utilize logistic regression with more than two classes?

Because logistic regression is a binary classifier, it cannot be used for more than two classes. Nave Bayes' Classifiers are better suited for multi-class classification methods like Decision Trees.


I hope that this set of Machine Learning Interview Questions and Answers will aid you in your preparation for the Machine Learning interview test and as well as while hiring the Machine Learning engineer for your company.

Best wishes! 

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Soujanya Varada
Soujanya Varada
As a technical content writer and social media strategist, Soujanya develops and manages strategies at iMocha. With strong technical background and years of experience in content management, she looks for opportunities to flourish in the digital space. Soujanya is also a dance fanatic and believes in spreading light!
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Topics: Tech Recruitment

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