Data analyst interviews
Data analyst interview
The questions graduate and junior data analyst interviews ask, grouped the way interviews use them, each with a free guide to what it’s really asking. Then practise them out loud, and try the coding part in your browser.
66 questions with answer guides58 coding challenges, free in your browserA 20-day study plan
The short answer
Graduate data analyst interviews usually ask about you and why you want the job, then technical questions you answer out loud (joins, cleaning data, simple statistics, charts and explaining a result), and often a live SQL task or a short case. Practise all three: the spoken answers on camera or with an AI interviewer, and the SQL in your browser.
What the interview covers
Most graduate and junior data analyst interviews have three parts. First, questions about you: your background, why you want the job and examples of how you work. Second, technical questions you answer out loud: joining and cleaning data, simple statistics, choosing a chart, and explaining a result to someone who doesn’t work with data. Third, often a live SQL task, a take-home exercise or a case study, and at some employers a short presentation of an analysis at an assessment day.
The questions below follow those parts. Each one has a guide to what the interviewer is listening for, how to structure your answer and an example outline. For what each stage involves and how technical tests are run, read what each stage of a data analyst interview involves on Deeplink Coaching, and if you want a timed check of your SQL first, take the free 20-minute SQL and skills test on Deeplink Toolkit.
Want a day-by-day route through these questions and the coding part? Follow the four-week data analyst interview plan
How to prepare
Learn what each question is testing
Read the guides below, starting with the technical questions you’d answer out loud.
See the questionsGet one project ready to talk through
Most data interviews spend longest on a project you’ve done: what the question was, what you did with the data, and what changed.
How to talk through a data projectWarm up the SQL
Write and run real queries on realistic data, then say out loud what each part does.
SQL interview questions to practisePractise out loud, against the clock
Answer a set of data analyst questions on camera, or with an AI interviewer that asks follow-ups, and read your feedback.
See a sample report
Questions for other data roles
- Data engineer interview questionsData engineer interviews
- Product analyst interview questionsProduct analyst interviews
- Finance data analyst interview questionsBanking, insurance and fintech
- Healthcare data analyst interview questionsNHS and healthcare
- Retail data analyst interview questionsRetail and e-commerce
The questions
Grouped the way
Technical questions to answer out loud
SQL, cleaning data, statistics, charts and explaining results, as you’d say them to an interviewer.
- Explain the difference between an inner join and a left join, as if you were talking to a manager who doesn’t use SQL.SQL · 2 minutes to answer
- You’re given a messy spreadsheet of customer orders. Talk me through how you’d clean it before analysing it.Data preparation · 2 minutes to answer
- What’s the difference between correlation and causation? Give an example from real life.Statistics · 1 minute 30 seconds to answer
- How do you decide which chart to use to show a result, and what mistakes do you try to avoid?Data visualisation · 2 minutes to answer
- A stakeholder asks you for “all the data” on customers. How do you find out what they really need?Stakeholders · 2 minutes to answer
- A query you wrote is running very slowly. What would you check first?SQL · 1 minute 30 seconds to answer
- A colleague says a rise in click-through rate from 2.0% to 2.3% is “significant”. What would you ask before agreeing?Statistics · 2 minutes to answer
- A headline says a bus route’s punctuality “rose 5%” when the share of buses on time went from 80% to 84%. Is that fair, and how would you rewrite it?Numeracy · 1 minute 30 seconds to answer
- Explain what a window function does, using a football league table as your example and no code at all.SQL · 2 minutes to answer
- You have two customer lists from different systems and no shared ID. How would you match them, and how would you know how well you’d done?Data preparation · 2 minutes to answer
- Someone emails you a spreadsheet ten minutes before a meeting and asks for the headline number. What checks would you run first?Data quality · 2 minutes to answer
- Explain what a p-value does and doesn’t tell you, to a shop manager deciding whether to keep a new store layout.Statistics · 2 minutes to answer
- Here’s a query: SELECT customers.name, COUNT(*) AS orders FROM customers LEFT JOIN orders ON orders.customer_id = customers.id GROUP BY customers.name. Tell me in plain English what it returns, and one way it could give the wrong answer.SQL · 2 minutes to answer
- When would you do a piece of analysis in Excel, when in SQL and when in Python? Give an example of each.Tools · 2 minutes to answer
- Describe the one-page dashboard you’d build for a café owner who checks it on her phone once a day.Dashboards · 2 minutes to answer
- A director wants a pie chart with fourteen slices on the front page of a report. How do you respond?Data visualisation · 1 minute 30 seconds to answer
Cases and metrics
Working through a business question with numbers: what you’d measure, what you’d check and what you’d recommend.
- A dashboard shows sales fell 20% last week. How would you work out why?Analytical thinking · 2 minutes 30 seconds to answer
- A chain of 20 cafés has kept its sales at £10 million a year, but its profit has fallen from £1 million to £400,000 in two years. Staff costs rose by £400,000 and ingredients by £200,000; other costs didn’t change. What would you look into, and what would you recommend?4 minutes to answer
- A company sells a scheduling app to small businesses for £10 per user per month and has 50,000 paying users. Each user costs about £2 a month to serve. It’s thinking of raising the price to £12. How would you decide whether it should?4 minutes to answer
- An airline flies a 180-seat plane on a domestic route twice a day. On average it sells 117 seats per flight at £60 each, and each flight costs £8,000 to run. Is the route making money, and how could it be improved?4 minutes to answer
- Hospital A sees 82% of its A&E patients within four hours, and Hospital B only 74%. Yet B does better for major cases, 60% against 50%, and for minor cases, 95% against 90%. How can both be true, and what would you report?4 minutes to answer
- Your dashboard says online sales last month were £2.4 million, but the finance team’s report says £2.2 million. How would you find out why the two figures differ, and what would you do about it?4 minutes to answer
- A library service has moved bookings for its 40 study rooms online. Before, people booked by phone or at the desk, and about a quarter of booked slots went unused. Which three measures would you track to see whether the change is working, and why those three?4 minutes to answer
- A charity wants to test whether a shorter online donation form raises more money. The form gets about 8,000 visitors a month, 5% of them donate, and the average gift is £30. How would you design the test, and how would you decide when to stop it?4 minutes to answer
- A council wants to know which neighbourhoods need more recycling bins. It has a year of collection records, showing how full each bin was when it was emptied, and 2,000 complaints about overflowing bins. How would you approach it?4 minutes to answer
- A shopping centre had 1.2 million visits last December. So far this year, footfall has been about 4% below the same month last year. How would you forecast this December, and how would you show the manager how uncertain your forecast is?4 minutes to answer
Presenting an analysis
A short written brief with figures, 10 minutes to prepare and 5 to present, as at an assessment day.
- You’re a graduate analyst at a chain of 12 bookshops. Sales have fallen from £9 million to £7.6 million in three years, and only 3% of them are online. The managing director has £250,000 to invest and three ideas: a better website with click and collect; cafés in the four busiest shops, which make half of all sales; or author events and children’s reading clubs, since event visitors spend twice as much. Prepare a five-minute presentation recommending how to spend it.5 minutes to answer
- You’re a graduate analyst at a chain of 30 bakeries. The bread and cakes it throws away cost £1.2 million a year to make. Waste is 22% of what’s baked in its eight railway station shops and 11% in the other 22 shops. The operations director has three ideas: half price on everything left after 5pm, which cut waste at two station shops from 22% to 13% in a four-week trial, though full-price sales there dipped; baking twice a day in smaller batches, which needs £5,000 of equipment per shop and which the head baker expects to cut waste by a third; or giving leftovers to a food charity, which costs nothing but saves no money. Prepare a five-minute presentation recommending what the chain should do.5 minutes to answer
- You’re a graduate analyst at a hospital trust. Last year 36,000 of its 400,000 outpatient appointments, 9%, were missed without warning, up from 6% three years ago. The trust estimates each one wastes £120 of clinic time. Missed appointments are highest among 18 to 30 year olds (15%) and for slots before 9am (13%). In a three-month trial, text reminders sent two days before cut missed appointments in the skin clinic from 10% to 6%. Texts cost 4p each, and the trust has mobile numbers for 80% of patients. An online system for patients to cancel and rebook would cost £90,000 to set up. Prepare a five-minute presentation recommending what the trust should do.5 minutes to answer
- You’re a graduate analyst at an energy supplier with 300,000 customers. Calls to its helpline rose from 40,000 to 52,000 a month this winter, and the average wait is now 14 minutes. Of those calls, 45% are about bills, 25% about meter readings, 15% about moving home and 15% about other things. Two thirds of the meter reading calls come from customers without a smart meter. The customer director has £500,000 and three options: 15 more call handlers for a year (£450,000); a better online account where customers can send readings and see their bill explained (£350,000); or a campaign to book smart meter fittings for the 20,000 customers who call most (£150,000). Prepare a five-minute presentation recommending what to do.5 minutes to answer
- You’re a graduate analyst at a bus company that can add two buses to its network from January, at £150,000 a year each. Route 3 carries 2,400 passengers a day but runs on time only 74% of the time, mostly because of roadworks due to finish in March. Route 11 carries 1,500 a day, and at peak times about 120 people a day are left at stops because buses are full. Route 20, a new route to a business park, carries 300 a day and has grown by 10% a month since it started in June. The average fare is £2. Prepare a five-minute presentation recommending where the two buses should go.5 minutes to answer
- You’re a graduate analyst at a personal loans company. About 4,000 customers a month miss a payment, and every one of them is phoned, at £12 a call. 60% pay within 30 days, and the company’s analysis suggests most of them would have paid without a call. Of the rest, about 400 a month end up in default, costing an average of £1,500 each. The collections director has three ideas: a text with a link to pay, at 20p each, sent before any call; a model that predicts who will pay without help, so that only the others are phoned, costing £60,000 to build; or a specialist team of six for customers in financial difficulty, costing £240,000 a year. Prepare a five-minute presentation recommending what to do.5 minutes to answer
- You’re a graduate analyst at an online fashion retailer. It sold 2 million items last year, and 30% were returned, up from 25% the year before. Each return costs £5 to process. Dresses are returned 45% of the time and all other items 20%, and dresses have grown from a fifth to two fifths of the items it sells. Half of all returns are for poor fit. The customer director has three ideas: charging £1.50 for each return, although a third of customers in a survey said they’d then shop less; a size advice tool costing £250,000 a year, which cut fit returns on dresses by a fifth in a trial; or better measurements and photos for the 200 most-returned products, which account for a fifth of returns, costing £80,000 once. Prepare a five-minute presentation recommending what to do.5 minutes to answer
Tools and ways of working
Dashboards people use, moving work out of spreadsheets, version control, scheduling, documentation and checking SQL an AI assistant wrote.
- Six months ago you built a dashboard for the sales team, and the usage figures show hardly anyone opens it. What do you do?1 minute 30 seconds to answer
- Tell me about a time you replaced a manual task, such as a spreadsheet updated by hand, with a query or a script. How did you make sure the new version was right?Initiative · 2 minutes to answer
- Why should analysts use version control for their queries and scripts, and what does good practice with it look like day to day?Ways of working · 2 minutes to answer
- Explain how you’d organise a team’s SQL transformations into layers, with tests, so that people can trust the tables they use.Data quality · 2 minutes to answer
- A report must be refreshed by 6am every day. How would you schedule it, and set up alerts so problems are caught without flooding people with messages?Pipelines · 2 minutes to answer
- You’ve built a dataset that other analysts will use. What would you write down about it, and how would you keep that documentation useful?Ways of working · 2 minutes to answer
- You’re going on three weeks’ leave tomorrow, and a colleague will run your weekly report while you’re away. How do you hand it over?1 minute 30 seconds to answer
- An AI assistant writes you a SQL query that runs without errors and returns a plausible number. How would you check it before you use the result?SQL · 2 minutes to answer
- How would you test a SQL transformation before it goes into production?Data quality · 2 minutes to answer
- Tell me about a time you inherited code or a spreadsheet that nobody understood. How did you make sense of it?Problem solving · 2 minutes to answer
Behavioural questions about data work
“Tell me about a time…” questions, with examples from data work.
- Tell me about a time you caught a mistake that others had missed. How did you find it, and what happened next?Attention to detail · 2 minutes to answer
- Describe a time you had to explain something complicated to someone without your background. How did you make sure they understood?Communication · 2 minutes to answer
- Describe a problem you solved where the answer wasn’t obvious. How did you work out what to do?Problem solving · 2 minutes to answer
- Describe a time you had to learn something new quickly. How did you go about it?Learning · 2 minutes to answer
- Tell me about a time you disagreed with a teammate about how to build or fix something. How did you resolve it?Teamwork · 2 minutes to answer
- You realise a spreadsheet your team sent to a client yesterday contains an error you made. What do you do?1 minute 30 seconds to answer
- Tell me about a time you told someone you weren’t confident in a result they wanted to use straight away. What happened?Integrity · 2 minutes to answer
- Tell me about a time you turned down, or reshaped, a request for analysis. What did you offer instead?Judgement · 2 minutes to answer
- Tell me about a time you had to decide whether to use a piece of personal data at all, not just how to keep it safe.Integrity · 2 minutes to answer
- Tell me about a time something you built broke after it went live. How did you find out, and what did you change afterwards?Resilience · 2 minutes to answer
- Tell me about a time you chose between a quick fix and a proper one. Would you make the same choice again?Decision making · 2 minutes to answer
- Describe a time you explained a technical limit to someone who just wanted the data sooner. How did you handle it?Communication · 2 minutes to answer
- Tell me about a time your analysis changed what someone decided to do. How did you make the case?Influencing · 2 minutes to answer
First-round questions
About you and why you want the job: usually the first questions, often on a one-way video.
- Tell me about yourself and what has brought you to apply for this role.2 minutes to answer
- Why do you want this role, and what do you think it will involve day to day?2 minutes to answer
- Why do you want to work for us rather than one of our competitors?2 minutes to answer
- What kinds of tasks give you energy, and why?1 minute 30 seconds to answer
- Describe a really good day at university or work. What made it good?1 minute 30 seconds to answer
- Your manager needs a report by 5pm, but the data you depend on won’t arrive until 4pm. What do you do?1 minute 30 seconds to answer
- Why do you want to work in data? What first got you interested, and what have you done since to find out whether the work suits you?2 minutes to answer
- In about a minute, describe one piece of data work you’ve done: what you were trying to find out, and what came of it.Portfolio · 1 minute to answer
- What would you most want to learn in your first year as an analyst, and how would you go about learning it?1 minute 30 seconds to answer
- Pick a business you know as a customer, such as a supermarket, a bank or a streaming service. How do you think it uses data to make decisions, and where could it use data better?Commercial awareness · 2 minutes to answer
The coding part
Practise the live task
A first set of original SQL and pandas questions like the live task, easiest first, with realistic data: write your answer, run it and check it against hidden tests. Free, with no account needed.
- Top three customers by spendSQL · Easy · about 10 minutes
- Fix the AI’s no-show reportSQL · Easy · about 10 minutes
- Monthly online revenuepandas · Easy · about 12 minutes
- Top two sellers in each shopSQL · Medium · about 12 minutes
- Fix a merge that double countspandas · Medium · about 15 minutes
- Month-one retention by cohortSQL · Hard · about 18 minutes
Interview guides
Read
In-depth guides for data analyst interviews, with worked answers and a practice checklist.
- 7 min read
How to talk through a data project in an interview
A five-part structure, a worked example, a one-minute version and the follow-ups you’ll get.
- 7 min read
How to explain your SQL out loud in an interview
What to say before, during and after a live SQL task, and how to recover from a mistake.
- 7 min read
Changing career into data: how to answer the interview questions
The questions career changers get, what’s behind each, and worked answers from three careers.
Still deciding on the route in? Read how to become a graduate data analyst on Deeplink Coaching.