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Day 9 — What *R*² can and cannot sayYear 12 Maths · T1 W1–2 · Day 9 lesson

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Year 12 / Mathematics / Term 1 / Weeks 01 02

Part of the full two-week lesson sequence. Check the pack guide and taught point before teaching.

Open for this lesson: Pack guide.

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Teacher copy: This page may include teaching prompts or answer keys. Answer keys in this public library can be viewed by anyone. Give learners a clean prompt, use checks as formative evidence, and change a case locally when prior access matters.

Success: Square r and interpret R² as a descriptive measure of a straight-line fit for the observed pairs.

  1. Notice · 3 min. Ask why squaring +0.9189 cannot tell the direction on its own.
  2. Model · 5 min. Compute R² ≈ 0.8444 using unrounded r where possible, then convert to about 84.4%.
  3. Try · 6 min. Learners use their technology output to calculate the square; compare rounding differences. Provide the precomputed r only if needed and record that support.
  4. Compare · 5 min. Say “About 84.4% of the observed variation in visit counts is accounted for by a straight-line relation with trial hours in these six invented pairs.” Reject “84.4% of visits are caused by hours.”
  5. Transfer · 4 min. Students identify one unmeasured factor, such as publicity or weather, as a possible alternative, without asserting it occurred.
  6. Exit · 2 min. Collect R² and one bounded sentence. If a learner gives 0.9189 as R², revisit square versus input.