Data analyst interview questions, with answer tips

Data analyst interviews test whether you can get the right numbers out of messy data, and whether you can turn them into something a busy manager will act on. Here are the questions to expect and how to answer them.

Updated 26 October 2026 · 4 min read

What to expect

Most processes include a screening call, a technical test (usually SQL and sometimes Excel), a task or case study where you analyse a dataset and present findings, and a competency interview. Junior roles focus more on the technical basics; senior roles on judgement, stakeholders and impact.

SQL and Excel questions

Write a query to find the top five customers by revenue last month.Filter on dates first, GROUP BY customer, SUM revenue, ORDER BY and LIMIT. Mention how you'd handle refunds or ties.
What's the difference between WHERE and HAVING?WHERE filters rows before grouping; HAVING filters groups after aggregation.
How would you calculate a running total or month-on-month change?Window functions: SUM() OVER (ORDER BY month), and LAG() for the previous month.
How do you find and remove duplicate records?Define what makes a duplicate first, then GROUP BY with HAVING COUNT(*) > 1, or ROW_NUMBER() to keep one.
When would you use XLOOKUP or a pivot table?XLOOKUP to bring data together from another table; pivots to summarise quickly. Know their limits on large data.

Statistics and analysis questions

What's the difference between mean and median, and when does it matter?Median is robust to outliers. Give an example such as salaries or order values.
What does correlation not tell you?Causation. Mention confounding factors and how an experiment or control group helps.
How would you check whether a sudden drop in sales is real?Check the data pipeline and definitions first, then compare to seasonality, segments and external events.
How do you make sure your numbers are right before sharing them?Reconcile to a known total, sense-check against last period, peer review and document assumptions.

Dashboard and communication questions

How do you decide what goes on a dashboard?Start from the decisions users make. Keep the few metrics that drive them, and put detail behind a click.
Tell me about a dashboard or report you built that people actually used.Who it was for, what decision it supported and how you knew it was used.
How would you present findings to a non-technical manager?Lead with the answer and what to do about it, then the evidence, in plain language.

Behavioural questions

Tell me about a time your analysis changed a decision.Your strongest story. Use STAR and quantify the outcome.
Describe a time you found a mistake in data or a report.How you spotted it, how you raised it and what you changed to stop it happening again.
How do you handle lots of ad hoc requests?Prioritising by impact and urgency, and being open about trade-offs.
Tell me about a time a stakeholder disagreed with your numbers.Listening, checking your work and explaining with evidence. See our conflict guide.

Example answer: "Tell me about a time your analysis changed a decision."

SituationOur marketing team planned to cut email campaigns because overall open rates had fallen for six months.

TaskI was asked to confirm the decline before they cut the budget.

ActionI broke open rates down by customer segment and email type and found the drop was almost entirely among customers on one email provider. I checked with our email platform and confirmed a change in how that provider reported opens had started in the same month. I then re-ran the analysis using clicks, which weren't affected, and showed engagement had actually been stable. I presented this on one slide with a recommendation to track clicks as the main metric.

ResultThe team kept the campaign budget and switched their main metric to clicks. Six months later, email was still one of their best-performing channels.

Tips

Practise SQL out loud. Talking through your logic as you write is often assessed as much as the query itself.
Bring a portfolio project you can explain in two minutes: the question, the data, what you found and what it meant.
In case tasks, state your assumptions and finish with a recommendation, not just charts.

Frequently asked questions

What questions are asked in a data analyst interview?

Usually SQL questions, sometimes Excel, basic statistics, questions about dashboards and presenting findings, a case study or data task, and competency questions about working with stakeholders.

How do I prepare for a data analyst SQL test?

Practise joins, GROUP BY with HAVING, date filtering, and window functions such as ROW_NUMBER, LAG and running totals. Talk through your logic as you go.

What's the difference between a data analyst and a data scientist interview?

Data analyst interviews focus more on SQL, reporting, dashboards and communicating insights. Data scientist interviews add machine learning, deeper statistics and modelling case studies.

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