Tell me about a data project you worked on. What question were you answering?

Note: Lead with the question, not the tools. "I used Python and SQL" describes a toolkit; "we could not tell which customers were about to churn" describes a problem worth solving.

Structure it as:

• The business question and who was asking it. Someone had to be waiting on the answer — say who, and what decision depended on it.
• The data. Where it came from, how much, and what was wrong with it. Realistically most of the work was here, and saying so is credible rather than a weakness.
• Your approach, briefly. The analysis or model, and — importantly — why that approach rather than a simpler one.
• The finding and what changed. An analysis nobody acted on is not a result. If it led nowhere, be honest about why, because that is a common and instructive experience.

If you found the data was unreliable and that was the real finding, tell that story. It happens constantly and few people report it.