Author note — to cover

Calculate the mean of an ungrouped list as total divided by count, including decimal answers and means of measurements, and show one extreme value dragging the mean towards it. Interpret the result in context. Frequency-table and grouped versions are later pages; reverse problems live on Working backwards from the mean. Both tiers. (S4)

• Fluency — direct questions on the mean, 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).