Author note — to cover

Define the population as everyone of interest and the sample as the subset actually surveyed, with questions naming both precisely in context. Include why sampling is used at all. Methods of selection belong to the random and non-random sampling pages; stratified sampling is not in 9-1 GCSE and lives at A level. Both tiers. (S1)

• Fluency — direct questions on populations and samples, 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).