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Data Analyst interview questions
Data analyst interviews test whether you can turn a vague business question into a clear answer. SQL gets you through the door; explaining what the numbers mean gets you the job.
What interviewers look for
- SQL and spreadsheets. Getting the right data quickly.
- Business sense. Asking what decision the analysis supports.
- Communication. Explaining findings to people who don't read charts for fun.
How the interview usually runs
- Recruiter call.
- SQL or Excel test.
- Case study or take-home analysis.
- Interview with the hiring manager and stakeholders.
Stages vary by company, so ask the recruiter what to expect before you start preparing.
10 Data Analyst interview questions, and how to answer them
1. Write a query for monthly active users.
What they want to see: SQL basics in a real setting.
How to answer: Use COUNT(DISTINCT user_id) grouped by month, and define what "active" means.
2. Sales fell 10% last month. How do you investigate?
What they want to see: Structured thinking.
How to answer: Check data quality first, then split by product, region and channel to find where it fell.
3. INNER JOIN or LEFT JOIN?
What they want to see: Avoiding silent data loss.
How to answer: Explain how each treats unmatched rows and how to check row counts.
4. How do you explain a chart to an executive?
What they want to see: Communication.
How to answer: Lead with the conclusion and the action, then show the evidence.
5. What makes a good dashboard?
What they want to see: Design judgement.
How to answer: A small number of metrics tied to decisions, clear definitions and sensible comparisons.
6. Mean or median?
What they want to see: Basic statistics.
How to answer: Use the median with skewed data such as income or order value.
7. How do you handle missing data?
What they want to see: Care with quality.
How to answer: Find out why it's missing, then filter, fill or flag it, and state what you did.
8. How would you check an A/B test result?
What they want to see: Applied statistics.
How to answer: Check sample size, randomisation, significance and whether the effect matters in practice.
9. A stakeholder disagrees with your numbers.
What they want to see: Stakeholder handling.
How to answer: Reconcile definitions together and check the source before defending your result.
10. Tell me about an analysis that changed a decision.
What they want to see: Impact.
How to answer: Give the question, your finding and what the business did.
A sample answer
Sales fell 10% last month. How do you investigate?
First I'd confirm the data is complete. In a similar case, tracking was fine and the drop was real. Splitting by channel showed nearly all of it came from one paid campaign that had been paused. Other channels were flat. I shared that with marketing in one slide, they restarted a smaller campaign, and sales recovered the following month.
A made-up example to show the structure. Use your own experience and real numbers.Common mistakes
- Jumping into SQL without clarifying the question.
- Presenting a table instead of a conclusion.
- Not checking row counts after joins.
- Confusing correlation with cause.
Practise this out loud
Run a mock interview for a Data Analyst role. Questions change every time, you answer by voice or typing, and each answer gets a score with feedback.
Frequently asked questions
What tools should a data analyst know?
SQL and Excel are the core, plus one BI tool such as Power BI or Tableau. Python is a useful extra.
How do I prepare with no experience?
Do a project on public data, write up what you found and what you'd recommend, and treat it like a work example in interviews.