Author note — to cover

Cover systematic sampling (every nth from a list) and opportunity or convenience sampling; questions name the method used and identify who gets missed. Naming and critiquing only, no calculations. Stratified and quota sampling are out, beyond 9-1 GCSE; stratified reappears at A level. Bias itself is the sibling page. Both tiers. (S1)

• Fluency — direct questions on non-random sampling, 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).