Paper 2 · Statistics
⏱ Tested in 3 exam questions since 2016
Lesson 12 of 21
Statistics 12 z-scores 4
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- Find 'between' probabilities with P(a ≤ z ≤ b) = P(z ≤ b) − P(z ≤ a)
- Combine the complement and negative-z tricks inside one two-sided calculation
- Memorise the anchor P(−1.96 ≤ z ≤ 1.96) = 0.95 for all later inferential work
- Default to z-tables at HL — the empirical rule only when the question says so
Most recent exam questions
- 2021 Paper 2 Q8(a)(i) — inverse normal — find the z-score with P(Z ≤ z) = 0.90, then convert back to a raw score
- 2017 Paper 2 Q8(a)(ii) — inverse normal — given a tail probability, find the corresponding z-value, then de-stand…
- 2016 Paper 2 Q9(a)(ii) — inverse standardisation — given a cumulative probability, find the data value
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