Free practice · single-choice · hard
Practice
Diagnose an average-of-averages error
Why is (8 hours + 20 hours) ÷ 2 = 14 hours not the correct overall average for regions with 40 and 10 tickets?
Order extract · structure card
One row per order, with every field assigned a role
- Observation
- One completed or open order
- Candidate key
- order_id · complete and unique
- Measure
- revenue · quantitative · USD
- Dimensions
- order_date, region, refunded
The row grain and candidate key must be verified before revenue is summarized or tables are joined.