Author note — to cover (Higher)

Higher only. Read a cumulative frequency curve: estimate the median at n over 2, quartiles at n over 4 and 3n over 4, the interquartile range, and how many values lie above or below a given value. Stress these are estimates. Quartile definitions live on Averages and spread; box plots drawn from the curve are the sibling page. (S3, S4)

• Fluency — direct questions on reading a cumulative frequency graph, 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).