Skill readiness test

Applied Signal Processing and AI/ML Engineer at Johns Hopkins Applied Physics Laboratory

2 questions, about 3 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. 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

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

pandas flask requests pytest