Skill readiness test — Senior Data Analyst

11 questions, about 7 minutes. This is a diagnostic, not a certification — it estimates your skill readiness, it does not guarantee you are qualified for or will be hired into this role.

1. Which is the correct way to lock a cell reference so it does not shift when copied across a row?

$A1 A$1 $A$1 A1$

2. A query aggregates revenue by region but SELECT also lists an ungrouped column. What happens on strict SQL engines (e.g. MySQL with ONLY_FULL_GROUP_BY, or PostgreSQL)?

It runs and picks an arbitrary value for the ungrouped column It errors — every selected column must be aggregated or in GROUP BY It silently returns NULL for the ungrouped column It automatically adds the column to GROUP BY

3. What does `df.groupby('region')['sales'].sum()` return?

The total sales across the whole dataframe Total sales summed for each distinct region A count of rows per region An error, because groupby requires two columns

4. In Power BI, what is the main purpose of a DAX measure versus a calculated column?

Measures compute dynamically per visual context; calculated columns are stored per row They are identical in every way Calculated columns can only be text Measures cannot use aggregation functions

5. Which library is most commonly used for tabular data manipulation in Python?

pandas flask requests pytest

6. Which clause filters rows before they are grouped by GROUP BY?

HAVING WHERE ORDER BY LIMIT

7. An INNER JOIN between orders and customers drops rows where...

the customer has no matching order the order has no matching customer both a and b nothing is dropped

8. Two tables are related on a shared key but the relationship shows a dotted line in the model view. What does that usually mean?

The relationship is inactive The tables are identical The relationship is many-to-many by definition There is a syntax error

9. You need each customer's most recent order. Which approach is most reliable?

ORDER BY order_date DESC LIMIT 1 with no grouping A window function (ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC)) MAX(order_date) alone with SELECT * GROUP BY customer_id with no aggregate on the other columns

10. Which function looks up a value in one column and returns a value from another column in the same row, matching on the leftmost column?

VLOOKUP CONCAT SUMIF TRANSPOSE

11. A pivot table field summarizes as SUM by default but the underlying column has some text values mixed in. What is the most likely visible symptom?

Excel crashes The field silently switches to COUNT instead of SUM The text values are converted to 0 automatically Nothing changes

Senior Data Analyst at WRK DIGITAL LTD