# Interview Questions for Data Science

In this Data Science Interview Questions blog, we are going to introduce you to the most frequently asked questions on **Data Science, Analytics and Machine Learning interviews**. This article is the perfect guide for you to learn all the concepts required to clear a Data Science interview. To get in-depth knowledge on Data Science.

Before moving ahead, you may go through the recording of Data Science Interview Questions where our instructor has shared his experience and expertise that will help you to crack any Data Science.

**What is Data Science?**

Data Science is a blend of various tools, algorithms, and machine learning principles with the goal to discover hidden patterns from the raw data.

**What is Selection Bias?**

Selection bias is a kind of error that occurs when the researcher decides who is going to be studied. It is usually associated with research where the selection of participants isn’t random. It is sometimes referred to as the selection effect. It is the distortion of statistical analysis, resulting from the method of collecting samples. If the selection bias is not taken into account, then some conclusions of the study may not be accurate.

**What are the different kernels functions in SVM?**

There are four types of kernels in SVM.

- Linear Kernel
- Polynomial kernel
- Radial basis kernel
- Sigmoid kernel

**What is pruning in Decision Tree?**

When we remove sub-nodes of a decision node, this process is called pruning or opposite process of splitting.

**Python or R – Which one would you prefer for text analytics?**

The best possible answer for this would be Python because it has Pandas library that provides easy to use data structures and high performance data analysis tools.

**What are Recommender Systems?**

A subclass of information filtering systems that are meant to predict the preferences or ratings that a user would give to a product. Recommender systems are widely used in movies, news, research articles, products, social tags, music, etc.

**What is Linear Regression?**

Linear regression is a statistical technique where the score of a variable Y is predicted from the score of a second variable X. X is referred to as the predictor variable and Y as the criterion variable.

**What is the difference between machine learning and deep learning?**

**Machine learning:**

Machine learning is a field of computer science that gives computers the ability to learn without being explicitly programmed. Machine learning can be categorised in following three categories.

- Supervised machine learning,
- Unsupervised machine learning,
- Reinforcement learning

**Deep learning:**

Deep Learning is a sub field of machine learning concerned with algorithms inspired by the structure and function of the brain called artificial neural networks.

**What is TF/IDF vectorization ?**

tf–idf is short for term frequency–inverse document frequency, is a numerical statistic that is intended to reflect how important a word is to a document in a collection or corpus. It is often used as a weighting factor in information retrieval and text mining. The tf-idf value increases proportionally to the number of times a word appears in the document, but is offset by the frequency of the word in the corpus, which helps to adjust for the fact that some words appear more frequently in general.

**Do gradient descent methods always converge to same point?**

No, they do not because in some cases it reaches a local minima or a local optima point. You don’t reach the global optima point. It depends on the data and starting conditions.

**What is an Eigenvalue and Eigenvector?**

Eigenvectors are used for understanding linear transformations. In data analysis, we usually calculate the eigenvectors for a correlation or covariance matrix. Eigenvectors are the directions along which a particular linear transformation acts by flipping, compressing or stretching. Eigenvalue can be referred to as the strength of the transformation in the direction of eigenvector or the factor by which the compression occurs.

**What is ‘Naive’ in a Naive Bayes ?**

The Naive Bayes Algorithm is based on the Bayes Theorem. Bayes’ theorem describes the probability of an event, based on prior knowledge of conditions that might be related to the event.

**What is Systematic Sampling?**

*Systematic sampling* is a statistical technique where elements are selected from an ordered sampling frame. In systematic sampling, the list is progressed in a circular manner so once you reach the end of the list, it is progressed from the top again. The best example of systematic sampling is equal probability method.

**Explain cross-validation.**

**Cross-validation** is a model validation technique for evaluating how the outcomes of statistical analysis will **generalize** to an **Independent dataset**. Mainly used in backgrounds where the objective is forecast and one wants to estimate how accurately a model will accomplish in practice.

The goal of cross-validation is to term a data set to test the model in the training phase (i.e. validation data set) in order to limit problems like overfitting and get an insight on how the model will generalize to an independent data set.

**What is the Supervised Learning?**

Supervised learning is the machine learning task of inferring a function from labeled training data. The training data consist of a set of training examples.

**Algorithms:** Support Vector Machines, Regression, Naive Bayes, Decision Trees, K-nearest Neighbor Algorithm and Neural Networks