Machine learning

  • Home
  • Interview_Question

Interview Questions & Answers

Select Series

What Is Machine Learning?

In answering this question, try to show you understand the broad applications of machine learning, as well as how it fits into AI. Put it into your own words, but convey your understanding that machine learning is a form of AI that automates data analysis to enable computers to learn and adapt through experience to do specific tasks without explicit programming.

What Is Kernel SVM?

Kernel SVM is the abbreviated version of the kernel support vector machine. Kernel methods are a class of algorithms for pattern analysis, and the most common one is the kernel SVM.

What Is Deep Learning?

This might or might not apply to the job you’re going after, but your answer will help to show you know more than just the technical aspects of machine learning. Deep learning is a subset of machine learning. It refers to using multi-layered neural networks to process data in increasingly complex ways, enabling the software to train itself to perform tasks like speech and image recognition through exposure to these vast amounts of data. Thus the machine undergoes continual improvement in the ability to recognize and process information. Layers of neural networks stacked on top of each for use in deep learning are called deep neural networks.

How Do Deductive and Inductive Machine Learning Differ?

Deductive machine learning starts with a conclusion, then learns by deducing what is right or wrong about that conclusion. Inductive machine learning begins with examples from which to conclude.

How Do You Choose an Algorithm for a Classification Problem?

The answer depends on the degree of accuracy needed and the size of the training set. If you have a small training set, you can use a low variance/high bias classifier. If your training set is large, you will want to choose a high variance/low bias classifier.

How Do Bias and Variance Playout in Machine Learning?

Both bias and variance are errors. Bias is an error due to flawed assumptions in the learning algorithm. Variance is an error resulting from too much complexity in the learning algorithm.

What Are Some Methods of Reducing Dimensionality?

You can reduce dimensionality by combining features with feature engineering, removing collinear features, or using algorithmic dimensionality reduction.

How Do Classification and Regression Differ?

Classification predicts group or class membership. Regression involves predicting a response. Classification is a better technique when you need a more definite answer.

What Is Supervised Versus Unsupervised Learning?

Supervised learning is a process of machine learning in which outputs are fed back into a computer for the software to learn from for more accurate results the next time. With supervised learning, the “machine” receives initial training to start. In contrast, unsupervised learning means a computer will learn without initial training.

What Is Decision Tree Classification?

A decision tree builds classification (or regression) models as a tree structure, with datasets broken up into ever-smaller subsets while developing the decision tree, literally in a tree-like way with branches and nodes. Decision trees can handle both categorical and numerical data.

What do you understand by selection bias?

It is a statistical error that causes a bias in the sampling portion of an experiment. The error causes one sampling group to be selected more often than other groups included in the experiment. Selection bias may produce an inaccurate conclusion if the selection bias is not identified.

Explain false negative, false positive, true negative and true positive with a simple example.

True Positive: If the alarm goes on in case of a fire. Fire is positive and prediction made by the system is true. False Positive: If the alarm goes on, and there is no fire. System predicted fire to be positive which is a wrong prediction, hence the prediction is false. False Negative: If the alarm does not ring but there was a fire. System predicted fire to be negative which was false since there was fire. True Negative: If the alarm does not ring and there was no fire. The fire is negative and this prediction was true.

What is the difference between Gini Impurity and Entropy in a Decision Tree?

Gini Impurity and Entropy are the metrics used for deciding how to split a Decision Tree. Gini measurement is the probability of a random sample being classified correctly if you randomly pick a label according to the distribution in the branch. Entropy is a measurement to calculate the lack of information. You calculate the Information Gain (difference in entropies) by making a split. This measure helps to reduce the uncertainty about the output label.

What is the difference between Entropy and Information Gain?

Entropy is an indicator of how messy your data is. It decreases as you reach closer to the leaf node. The Information Gain is based on the decrease in entropy after a dataset is split on an attribute. It keeps on increasing as you reach closer to the leaf node.

What are collinearity and multicollinearity?

Collinearity occurs when two predictor variables (e.g., x1 and x2) in a multiple regression have some correlation. Multicollinearity occurs when more than two predictor variables (e.g., x1, x2, and x3) are inter-correlated.

What is Cluster Sampling?

It is a process of randomly selecting intact groups within a defined population, sharing similar characteristics. Cluster Sample is a probability sample where each sampling unit is a collection or cluster of elements. For example, if you’re clustering the total number of managers in a set of companies, in that case, managers (samples) will represent elements and companies will represent clusters.

How is kNN different from kmeans clustering?

Don’t get mislead by ‘k’ in their names. You should know that the fundamental difference between both these algorithms is, kmeans is unsupervised in nature and kNN is supervised in nature. kmeans is a clustering algorithm. kNN is a classification (or regression) algorithm. kmeans algorithm partitions a data set into clusters such that a cluster formed is homogeneous and the points in each cluster are close to each other. The algorithm tries to maintain enough separability between these clusters. Due to unsupervised nature, the clusters have no labels. kNN algorithm tries to classify an unlabeled observation based on its k (can be any number ) surrounding neighbors. It is also known as lazy learner because it involves minimal training of model. Hence, it doesn’t use training data to make generalization on unseen data set.

While working on a data set, how do you select important variables? Explain your methods.

Following are the methods of variable selection you can use: Remove the correlated variables prior to selecting important variables Use linear regression and select variables based on p values Use Forward Selection, Backward Selection, Stepwise Selection Use Random Forest, Xgboost and plot variable importance chart Use Lasso Regression Measure information gain for the available set of features and select top n features accordingly.

What is the difference between covariance and correlation?

Correlation is the standardized form of covariance. Covariances are difficult to compare. For example: if we calculate the covariances of salary ($) and age (years), we’ll get different covariances which can’t be compared because of having unequal scales. To combat such situation, we calculate correlation to get a value between -1 and 1, irrespective of their respective scale.

Is it possible capture the correlation between continuous and categorical variable? If yes, how?

Yes, we can use ANCOVA (analysis of covariance) technique to capture association between continuous and categorical variables.