Below are some most commonly asked questions in the interviews.

Q1. What is data science and how is it different from other data-related fields?

Data Science is the domain of study that uses computational and statistical methods to get knowledge and insights from data. It utilizes techniques from mathematics, statistics, computer science and domain-specific knowledge to analyse large datasets, find trends and patterns from the data and make predictions for the future.

Data Science is different from other data related fields because it is not only about collecting and organising data. The data science process consists of analysing, modelling, visualizing and evaluating the data set. Data Science uses tools like machine learning algorithms, data visualisation tools and statistical models to analyse data, make predictions and find patterns and trends in the data.

Other data related fields such as machine learning, data engineering and data analytics are more focused on a particular thing like the goal of a machine leaning engineer is to design and create algorithms that are capable of learning from the data and making predictions, the goal of data engineering is to design and manage data pipelines, infrastructures and databases. Data analysis is all about exploring and analysing data to find patterns and trends. Whereas data science does modelling, exploring, collecting, visualizing, predicting, and deploying the model.

Overall, data science is a more comprehensive way to analyse data because it includes the whole process, from preparing the data to making predictions. Other fields that deal with data have more specific areas of expertise.

Q2. What is the data science process and what are the key steps involved?

A data science process also known as data science lifecycle is a systematic approach to find a solution for a data problem which shows the steps that are taken to develop, deliver, and maintain a data science project.

A standard data science lifecycle approach comprises the use of machine learning algorithms and statistical procedures that result in more accurate prediction models. Data extraction, preparation, cleaning, modelling, assessment, etc., are some of the most important data science stages. Key steps involved in data science process are −

Identifying Problem and Understanding the Business

The data science lifecycle starts with “why?” just like any other business lifecycle. One of the most important parts of the data science process is figuring out what the problems are. This helps to find a clear goal around which all the other steps can be made. In short, it”s important to know the business goal as earliest because it will determine what the end goal of the analysis will be.

Data Collection

The next step in the data science lifecycle is data collection, which means getting raw data from the appropriate and reliable source. The data that is collected can be either organized or unorganized. The data could be collected from website logs, social media data, online data repositories, and even data that is streamed from online sources using APIs, web scraping, or data that could be in Excel or any other source.

Data Processing

After collecting high-quality data from reliable sources, next step is to process it. The purpose of data processing is to ensure that any problems with the acquired data have been resolved before proceeding to the next phase. Without this step, we may produce mistakes or inaccurate findings.

Data Analysis

Data analysis Exploratory Data Analysis (EDA) is a set of visual techniques for analysing data. With this method, we may get specific details on the statistical summary of the data. Also, we will be able to deal with duplicate numbers, outliers, and identify trends or patterns within the collection.

Data Visualization

Data visualisation is the process of demonstrating information and data on a graph. Data visualisation tools make it easy to understand trends, outliers, and patterns in data by using visual elements like charts, graphs, and maps. It”s also a great way for employees or business owners to present data to people who aren”t tech-savvy without making them confused.

Data Modelling

Data Modelling is one of the most important aspects of data science and is sometimes referred to as the core of data analysis. The intended output of a model should be derived from prepared and analysed data.

At this phase, we develop datasets for training and testing the model for production-related tasks. It also involves selecting the correct mode type and determining if the problem involves classification, regression, or clustering. After analysing the model type, we must choose the appropriate implementation algorithms. It must be performed with care, as it is crucial to extract the relevant insights from the provided data.

Model Deployment

Model deployment contains the establishment of a delivery method necessary to deploy the model to market consumers or to another system. Machine learning models are also being implemented on devices and gaining acceptance and appeal. Depending on the complexity of the project, this stage might range from a basic model output on a Tableau Dashboard to a complicated cloud-based deployment with millions of users.

Q3. What is the difference between supervised and unsupervised learning?

Supervised Learning − Supervised learning is a type of machine learning and artificial intelligence. It is also called “supervised machine learning.” It is defined by the fact that it uses labelled datasets to train algorithms how to correctly classify data or predict outcomes. As data is put into the model, its weights are changed until the model fits correctly. This is part of the cross validation process. Supervised learning helps organisations find large-scale solutions to a wide range of real-world problems, like classifying spam in a separate folder from your inbox like in Gmail we have a spam folder.

Supervised Learning Algorithms − Naive Bayes, Linear regression, Logistic regression.

Unsupervised learning − Unsupervised learning, also called unsupervised machine learning, uses machine learning algorithms to look at unlabelled datasets and group them together. These programmes find hidden patterns or groups of data. Its ability to find similarities and differences in information makes it perfect for exploratory data analysis, cross-selling strategies, customer segmentation, and image recognition.

Unsupervised Learning Algorithms − K-means clustering

Q4. What is regularization and how does it help to avoid overfitting?

Regularization is a method that adds information to a model to stop it from becoming overfitted. It is a type of regression that tries to get the estimates of the coefficients as close to zero as possible to make the model smaller. In this case, taking away extra weights is what it means to reduce a model”s capacity.

Regularization takes away any extra weights from the chosen features and redistributes the weights so that they are all the same. This means that regularisation makes it harder to learn a model that is both flexible and has a lot of moving parts. A model with a lot of flexibility is one that can fit as many data points as possible.

Q5. What is cross-validation and why is it important in machine learning?

Cross-validation is a technique to test ML models by training them on different subsets of the available input data and then testing them on the other subset. We can use cross-validation to detect overfitting, ie, failing to generalise a pattern.

For cross-validation, we can use the k-fold cross-validation method. In k-fold cross-validation, we divide the data you start with into k groups (also known as folds). We train an ML model on all but one (k-1) of the subsets, and then we test the model on the subset that wasn”t used for training. This process is done k times, and each time a different subset is set aside for evaluation (and not used for training).

Q6. What is the difference between classification and regression in machine learning?

The major difference between regression and classification is that regression helps predict a continuous quantity, while classification helps predict discrete class labels. Some components of the two kinds of machine learning algorithms are also the same.

A regression algorithm can make a prediction about a discrete value, which is a whole number.

If the value is in the form of a class label probability, a classification algorithm can predict this type of data.

Q7. What is clustering and what are some popular clustering algorithms?

Clustering is a method for data mining that organises unlabelled data based on their similarities or differences. Clustering techniques are used to organise unclassified, unprocessed data items into groups according to structures or patterns in the data. There are many types of clustering algorithms, including exclusive, overlapping, hierarchical, and probabilistic.

K-means clustering is a popular example of a clustering approach in which data points are allocated to K groups based on their distance from each group”s centroid. The data points closest to a certain centroid will be grouped into the same category. A higher K number indicates smaller groups with more granularity, while a lower K value indicates bigger groupings with less granularity. Common applications of K-means clustering include market segmentation, document clustering, picture segmentation, and image compression.

Q8. What is gradient descent and how does it work in machine learning?

Gradient descent is an optimisation algorithm that is often used to train neural networks and machine learning models. Training data helps these models learn over time, and the cost function in gradient descent acts as a barometer to measure how accurate it is with each iteration of parameter updates. The model will keep changing its parameters to make the error as small as possible until the function is close to or equal to 0. Once machine learning models are tuned to be as accurate as possible, they can be used in artificial intelligence (AI) and computer science in powerful ways.

Q9. What is A/B testing and how can it be used in data science?

A/B testing is a common form of randomised controlled experiment. It is a method for determining which of two versions of a variable performs better in a controlled setting. A/B testing is one of the most important concepts in data science and the technology industry as a whole since it is one of the most efficient approaches for drawing conclusions regarding any hypothesis. It is essential that you comprehend what A/B testing is and how it normally works. A/B testing is a common method for evaluating goods and is gaining momentum in the area of data analytics. A/B testing is more effective when testing incremental changes such as UX modifications, new features, ranking, and page load speeds.

Q10. Can you explain overfitting and underfitting, and how to mitigate them?

Overfitting is a modelling error that arises when a function is overfit to a restricted number of data points. It is the outcome of a model with an excessive amount of training points and excessive complexity.

Underfitting is a modelling error that arises when a function does not properly match the data points. That is the outcome of a simple model with inadequate training points.

There are a number of ways that researchers in machine learning can avoid overfitting. These include: Cross-validation, Regularization, Pruning, Dropout.

There are a number of ways that researchers in machine learning can avoid underfitting. These include −

• Get more training data.

• Add more parameters or increase size of the parameters.

• Make the model more complex.

• Adding more time to training until the cost function is at its lowest.

With these methods, you should be able to make your models better and fix any problems with overfitting or underfitting.