Author note — to cover

Construct and read back-to-back stem-and-leaf diagrams: shared stems, left side read outwards, a key for each side. Questions extract the median and range of each side and make one comparison in context. Full comparison technique pairing average with spread lives on the Interpretation topic. Both tiers. (S4)

• Fluency — direct questions on back-to-back stem-and-leaf diagrams, limited to this lesson's stated scope (4 questions).
• Application — use the same skill in unfamiliar or contextual questions without introducing a later method (4 questions).
• Check — questions built around the exclusions and likely misconceptions named in the lesson brief (4 questions).