Statistics and SQL Screen

What they ask

For data roles in the Cairo office the technical round leans almost entirely on two things: statistics fundamentals and SQL. The interviewer alternates between short conceptual questions and small query exercises you talk through out loud.

Questions in this area, for example:

Statistics

• When is the median a better summary than the mean, and give a telecom example.
• Explain a p-value to a non-statistician without saying "probability of the null".
• You have KPI samples from two groups of cell sites; which test would you use to compare them and what assumptions are you making?

SQL, on a table alarms(site_id, severity, opened_at, closed_at):

1. Sites that raised more than five critical alarms last month.
2. Average time to close, per severity, for alarms that were actually closed.
3. For each site, the most recent alarm (one row per site).

Example

For item 3 the expected answer is a window function (ROW_NUMBER() OVER (PARTITION BY site_id ORDER BY opened_at DESC)) filtered to row 1; a GROUP BY with MAX(opened_at) alone loses the other columns, and they will point that out.

What they look for

• Comfortable, unhurried explanations of basic statistics; they care that you can reason about data, not recite formulas.
• Correct handling of NULL in closed_at, date arithmetic and grouping.
• Whether you ask about the size of the table before proposing a query, which signals real-world experience.