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Visit our Blogs & News portal or check out our recent posts below.
Our friends at Data Science Dojo have compiled a list of 101 actual Data Science interview questions that have been asked between 2016-2019 at some of the largest recruiters in the Data Science industry – Amazon, Microsoft, Facebook, Google, Netflix, Expedia, etc. Data Science is an interdisciplinary field and sits at the intersection of computer science, statistics/mathematics, and domain knowledge. To be able to perform well, one needs to have a good foundation in not one but multiple fields, and it reflects in the interview. They've divided the questions into six categories: Machine LearningData AnalysisStatistics, Probability, and MathematicsProgrammingSQLExperiential/Behavioural Questions Once you've gone through all the questions, you should have a good understanding of how well you're prepared for your next Data Science interview. Machine Learning As one will expect, Data Science interviews focus heavily on questions that help the company test your concepts, applications, and experience on machine learning. Each question included in this category has been recently asked in one or more actual Data Science interviews at companies such as Amazon, Google, Microsoft, etc. These questions will give you a good sense of what sub-topics appear more often than others. You should also pay close attention to the way these questions are phrased in an interview. Explain Logistic Regression and its assumptions.Explain Linear Regression and its assumptions.How do you split your data between training and validation?Describe Binary Classification.Explain the working of decision trees.What are different metrics to classify a dataset?What's the role of a cost function?What's the difference between convex and non-convex cost function?Why is it important to know bias-variance trade off while modeling?Why is regularisation used in machine learning models? What are the differences between L1 and L2 regularisation?What's the problem of exploding gradients in machine learning?Is it necessary to use activation functions in neural networks?In what aspects is a box plot different from a histogram?What is cross validation? Why is it used?Can you explain the concept of false positive and false negative?Explain how SVM works.While working at Facebook, you're asked to implement some new features. What type of experiment would you run to implement these features?What techniques can be used to evaluate a Machine Learning model?Why is overfitting a problem in machine learning models? What steps can you take to avoid it?Describe a way to detect anomalies in a given dataset.What are the Naive Bayes fundamentals?What is AUC - ROC Curve?What is K-means?How does the Gradient Boosting algorithm work?Explain advantages and drawbacks of Support Vector Machines (SVM).What is the difference between bagging and boosting?Before building any model, why do we need the feature selection/engineering step?How to deal with unbalanced binary classification?What is the ROC curve and the meaning of sensitivity, specificity, confusion matrix?Why is dimensionality reduction important?What are hyperparameters, how to tune them, how to test and know if they worked for the particular problem?How will you decide whether a customer will buy a product today or not given the income of the customer, location where the customer lives, profession, and gender? Define a machine learning algorithm for this.How will you inspect missing data and when are they important for your analysis?How will you design the heatmap for Uber drivers to provide recommendation on where to wait for passengers? How would you approach this?What are time series forecasting techniques?How does a logistic regression model know what the coefficients are?Explain Principle Component Analysis (PCA) and it's assumptions.Formulate Latent Semantic Analysis (LSA) and Latent Dirichlet Allocation (LDA) techniques.What are neural networks used for?40. Why is gradient checking important?Is random weight assignment better than assigning same weights to the units in the hidden layer?How to find the F1 score after a model is trained?How many topic modeling techniques do you know of? Explain them briefly.How does a neural network with one layer and one input and output compare to a logistic regression?Why Rectified Linear Unit/ReLU is a good activation function?When using the Gaussian mixture model, how do you know it's applicable?If a Product Manager says that they want to double the number of ads in Facebook's Newsfeed, how would you figure out if this is a good idea or not?What do you know about LSTM?Explain the difference between generative and discriminative algorithms.Can you explain what MapReduce is and how it works? If the model isn't perfect, how would you like to select the threshold so that the model outputs 1 or 0 for label?Are boosting algorithms better than decision trees? If yes, why?What do you think are the important factors in the algorithm Uber uses to assign rides to drivers?How does speech synthesis works? Data Analysis Machine Learning concepts are not the only area in which you'll be tested in the interview. Data pre-processing and data exploration are other areas where you can always expect a few questions. We're grouping all such questions under this category. Data Analysis is the process of evaluating data using analytical and statistical tools to discover useful insights. Once again, all these questions have been recently asked in one or more actual Data Science interviews at the companies listed above. What are the core steps of the data analysis process?How do you detect if a new observation is an outlier?Facebook wants to analyse why the "likes per user and minutes spent on a platform are increasing, but total number of users are decreasing". How can they do that?If you have a chance to add something to Facebook then how would you measure its success?If you are working at Facebook and you want to detect bogus/fake accounts. How will you go about that?What are anomaly detection methods?How do you solve for multicollinearity?How to optimise marketing spend between various marketing channels?What metrics would you use to track whether Uber's strategy of using paid advertising to acquire customers works?What are the core steps for data preprocessing before applying machine learning algorithms?How do you inspect missing data?How does caching work and how do you use it in Data Science? Statistics, Probability and Mathematics As we've already mentioned, Data Science builds its foundation on statistics and probability concepts. Having a strong foundation in statistics and probability concepts is a requirement for Data Science, and these topics are always brought up in data science interviews. Here is a list of statistics and probability questions that have been asked in actual Data Science interviews. How would you select a representative sample of search queries from 5 million queries?Discuss how to randomly select a sample from a product user population.What is the importance of Markov Chains in Data Science?How do you prove that males are on average taller than females by knowing just gender or height.What is the difference between Maximum Likelihood Estimation (MLE) and Maximum A Posteriori (MAP)?What does P-Value mean?Define Central Limit Theorem (CLT) and it's application?There are six marbles in a bag, one is white. You reach in the bag 100 times. After drawing a marble, it is placed back in the bag. What is the probability of drawing the white marble at least once?Explain Euclidean distance.Define variance.How will you cut a circular cake into eight equal pieces?What is the law of large numbers?How do you weigh nine marbles three times on a balance scale to select the heaviest one?You call three random friends who live in Seattle and ask each independently if it's raining. Each of your friends has a 2/3 chance of telling you the truth and a 1/3 chance of lying. All three say "yes". What's the probability it's actually raining? Explain a probability distribution that is not normal and how to apply that?You have two dice. What is the probability of getting at least one four? Also find out the probability of getting at least one four if you have n dice.Draw the curve log(x+10) Programming When you appear for a data science interview your interviewers are not expecting you to come up with a highly efficient code that takes the lowest resources on computer hardware and executes it quickly. However, they do expect you to be able to use R, Python, or SQL programming languages so that you can access the data sources and at least build prototypes for solutions. You should expect a few programming/coding questions in your data science interviews. You interviewer might want you to write a short piece of code on a whiteboard to assess how comfortable you are with coding, as well as get a feel for how many lines of codes you typically write in a given week. Here are some programming and coding questions that companies like Amazon, Google, and Microsoft have asked in their Data Science interviews. Write a function to check whether a particular word is a palindrome or not.Write a program to generate Fibonacci sequence.Explain about string parsing in R languageWrite a sorting algorithm for a numerical dataset in Python.Coding test: moving average Input 10, 20, 30, 10, ... Output: 10, 15, 20, 17.5, ...Write a Python code to return the count of words in a stringHow do you find percentile? Write the code for itWhat is the difference between - (i) Stack and Queue and (ii) Linked list and Array? Structured Query Language (SQL) Real-world data is stored in databases and it ‘travels’ via queries. If there's one language a Data Science professional must know, it's SQL - or “Structured Query Language”. SQL is widely used across all job roles in Data Science and is often a ‘deal-breaker’. SQL questions are placed early on in the hiring process and used for screening. Here are some SQL questions that top companies have asked in their Data Science interviews. How would you handle NULLs when querying a data set?How will you explain JOIN function in SQL in the simplest possible way?Select all customers who purchased at least two items on two separate days from Amazon.What is the difference between DDL, DML, and DCL?96. Why is Database Normalisation Important?What is the difference between clustered and non-clustered index? Situational/Behavioural Questions Capabilities don’t necessarily guarantee performance. It's for this reason employers ask you situational or behavioural questions in order to assess how you would perform in a given situation. In some cases, a situational or behavioural question would force you to reflect on how you behaved and performed in a past situation. A situational question can help interviewers in assessing your role in a project you might have included in your resume, can reveal whether or not you're a team player, or how you deal with pressure and failure. Situational questions are no less important than any of the technical questions, and it will always help to do some homework beforehand. Recall your experience and be prepared! Here are some situational/behavioural questions that large tech companies typically ask: What was the most challenging project you have worked on so far? Can you explain your learning outcomes?According to your judgement, does Data Science differ from Machine Learning?If you're faced with Selection Bias, how will you avoid it?How would you describe Data Science to a Business Executive? If you're looking for new Data Science role, you can find our latest opportunities here. This article was written by Tooba Mukhtar and Rahim Rasool for Data Science Jojo. It has been republished with permission. You can view the original article, which includes answers to the above questions here.
22. August 2019
By Laura Gayle, BusinessWomanGuide.org Smart technology is rapidly reshaping society. From cloud storage and mobile access to the internet of things and artificial intelligence, what was once regarded as science fiction is steadily becoming reality. In response, many employers are finding ways to modernize their workplaces by creating smart offices — not because it looks cool or is the trendy thing to do, but because they've discovered that doing so provides several tangible benefits. New devices, apps, and AI-driven tools can not only make your office smarter, they also can position you for better marketing and sales efforts and provide competitive advantages in your industry. Additionally, creating a smart office offers both employees and customers a seamless experience and can attract talented millennial workers. Since millennials naturally adapt to tech innovations, they can assist in this transition to bring your company to the next level. Here are five strategies to modernise your workplace with smart tech. 1. Use cloud-based storage Cloud-based storage offers both convenience and efficiency. Many among today's workforce probably don't even realise there was a time when offices were full of filing cabinets and computer equipment. Now that mobile access has been fully integrated into nearly all workplaces, much of the bulky equipment that previously took up space is disappearing. Filing cabinets? Paper files? Things of the past. Workers today don't typically spend hours every week filing stacks of papers because most documents are digitised and stored in the cloud. Other cloud-based technologies, such as remote workplaces and managed print services, are replacing old ways of conducting business. Cloud technology has been a significant game-changer for the office environment. Not only are files and documents stored on the cloud, but also businesses are using cloud-based platforms as a part of their services or customer experiences. Think about how much “software as a service” (a model in which software is licensed and accessed remotely instead of being downloaded on a user’s computer) has become a standardised part of doing business. This is all thanks to cloud technology. As time moves forward, expect it to continue making a significant impact on the modern workplace and customer experience. 2. Invest in voice-activated devices Various well-known gadgets found in "smart” homes or apartments are now making strides in the office setting, too. For example, voice-activated products such as Siri, Echo, Alexa, and Nest are commonly found in the workplace, adding functionality by offering a seamless user experience. Employees speak and the equipment automatically does what is asked — no more fiddling with equipment and trying to get things up and running manually. Voice-activated tech also allows workers to multitask and get things done faster, such as: Coordinating and syncing calendars Sending data requests Ordering supplies Reporting problems to the appropriate departments Streamlining IT requests These are just a handful of the many tasks voice-activated tech can perform. Businesses have steadily begun to include these types of products to make conference rooms even smarter. While this concept isn't mainstream in the office quite yet, it's not hard to image it becoming the norm within the next few years as this tech fully matures. Companies focused on modernising their workplaces are jumping on the proverbial bandwagon to get a leg up on the competition. These companies will be well ahead of the game when such tech initiatives do eventually become standard in the office. 3. Use tech to put offices in the comfort zone As modern offices evolve into open-space floor plans, they've become more informal and far more flexible. With that concept in mind, offices today are more focused on comfort — a stark contrast to the drab cubicle environments of yesteryear. Shifting to the open-design work environment has been a challenge for many; however, businesses are finding ways to make this transition easier through smarter tech. Solutions they are integrating into their spaces include: Hue lighting Virtual reality meeting rooms 360-degree video conferencing Keyless entry Smart tools not only appeal to workers because of their convenience and "coolness" factor; they also serve the practical purposes of enhancing comfort, personalising the remote experience, and even preventing repetitive stress injuries. 4. Integrate tech innovations to enhance the customer experience Businesses are investing in smart technology, and customers are reaping the benefits. As companies streamline their operations and customer service processes, customers are widely experiencing the convenience and simplicity associated with smart tech. Here are some features they currently enjoy: Chatbots for instant two-way communication AI-based customer learning opportunitiesPersonalised insights and recommendations Automation and custom ordering Cloud storage of customer information and preference history Many industries are relying on artificial intelligence to improve their services. Businesses that do not offer this level of tech to customers will soon find themselves unable to meet heightened consumer expectations. 5. Use AI to gain a competitive advantage Perhaps you don't want to go as far as microchipping your employees (yes, this is also a growing trend) or issuing them Segways, but there are a lot of other relatively new gadgets and AI-driven tools that can boost the "smartness" of your business — not to mention, amp up your competitive advantage. For instance, you can use AI to track the habits and patterns of your customer base while they spend time on your website and determine where they are in their "customer journey" with your brand. Armed with this information, you can customise their web experience, along with your communications to them. This personalisation can go a long way in your marketing efforts. After all, 80 percent of consumers say they are "more likely" to do business with a company that is able to give them a personalised experience. It's also important to know that research indicates customers want way more than basic personalisation. Using smart tech can easily help you bring things up to the next level. Smart tech adds significant value to the modern office in many ways. It's unwise to purchase tech because it's trendy, but when integrated with purpose and vision, many company decision-makers find this investment offers significant benefits and, in the end, pays off nicely. Harnham are the global leaders in Data & Analytics recruitment. Take a look at our latest roles or get in touch with one of our expert consultants to learn more.
09. January 2019
By Noam Zeigerson Noam Zeigerson is a Data & Analytics Executive and entrepreneur with over 16 years’ experience delivering Data solutions. What does the role of the CDO entail and how can we succeed? Researchers at Gartner estimate that 90 per cent of enterprises will have a ‘Chief Data Officer’ (CDO) in place by the end of 2019. It also predicts that by then only half of CDOs will have been successful. So, what does the role of the CDO entail and how can we succeed? The rise in the use of data in the enterprise to inform business decisions has led to a recent phenomenon - the Chief Data Officer. Organisations will have a CDO in place to handle the many opportunities and responsibilities that arise from industrial-scale collection and harnessing of data. Unfortunately, it is rare to be successful, due to a number of challenges. As a new role, the CDO need to be in a position to increase business efficiencies and improve risk management, especially since the General Data Protection Regulation (GDPR) came into effect in May 2018. This puts the CDO in a position where business expectations will be high, and we have to make tough and potentially unpopular decisions, because the CDO’s role sits at the crossroads of IT and business. We typically responsible for defining the data and analytics strategy at our organisation. The CDO becomes instrumental in breaking down siloed departments and data repositories, which makes information easier to find and also have ramifications for the IT team. As Gartner notes, many CDOs have faced resistance, but the successful ones are working closely with their Chief Information Officer (CIO) to lead change. To be a key part of any organisation’s digital transformation, the CDO need a wide range of skills. The skills required of a Chief Data Officer The role of the CDO is multifaceted. For this reason, CDOs need to be able to combine skills from the areas of data, IT, and business to be successful. Data skills: A background in data science is crucial. A passion for statistics and a clear understanding of how to interpret data to glean insights is core to the role of the CDO. The CDO then needs to be able to communicate what those insights mean in a business context and make information easily available to all. A knowledge of data security is also critical. In the UK, the Information Commissioner’s Office (ICO), whose job it is to enforce GDPR in the country, recommends the creation of a Data Protection Officer (DPO) at each organisation. This should fall within the remit of the CDO. The value of sharing data at a senior level is recognized by UK organisations, by and large. Further down the authority chain the picture is different, with about three-quarters of executive teams and nearly half of front-line employees actually need to have access to detailed data and analytics. The CDO needs to ensure that those who need data to further inform decision making can do so and are sufficiently trained to gain business insights from that data. IT skills: Understanding how information flows is an advantage as the CDO is well placed to recommend and implement technology to democratise and operationalise data, as well as improve security. The CDO will need to manage expectations across the enterprise, so appreciating what technology can deliver is the key. Artificial Intelligence (AI) and machine learning are going to feature heavily of UK data projects, so many CDOs need to get to grips fast with this technology. Business skills: Strategic business logic is essential to success as a CDO. If the expectation of the CDO is to influence strategy based on data, then consulting experience will be valuable. Project management skills is at the forefront of the CDO’s day-to-day role. Being able to bring siloed groups together and get them striving for the same common goal is a vital skill for any CDO. It’s clear that data analytics is only going to be deployed more heavily throughout the enterprise, so the CDO’s role is only going to become more influential and pivotal within organisations as different business units seek to gain insights to improve the business further. Making a success of the CDO role Every organisation will have different objectives and expectations of their CDO. Gartner estimates that four in every five (80 per cent) CDOs will have revenue responsibilities, meaning we will be expected to drive new value, generate opportunities, and also deliver cost savings. No pressure! Given those expectations, it’s no wonder that Gartner expects only half of CDOs to succeed. The core responsibilities of the CDO includes data governance and quality, and regulatory compliance. The CDO must also address the way that technology is deployed to address these issues. The CDO needs leadership and team building skills, as we are the chief change agent in the organisation for creating a data-driven culture. This means first-class communications skills will be valuable.The Chief Data Officer is going to be essential in delivering digital transformation. Organisations who create a CDO role must support that individual and make sure that they are integrated across departments, not isolated in a silo. The C-suite must lead from the front on this and, as we saw earlier, the support of the CIO will be critical. Harnham are the global leaders in Data & Analytics recruitment. Take a look at our latest roles or get in touch with one of our expert consultants to learn more.
08. November 2018