Author note — to cover (Higher)

Higher only. Motivate why unequal class widths make bar height dishonest and force frequency onto area; define frequency density as frequency divided by class width and calculate both ways, density from frequency and width, frequency from density and width. Table calculations only; drawing and reading histograms are the sibling pages. (S3)

• Fluency — direct questions on frequency density, 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).