A-LevelMathematicsProbability and statistics9709/62 · May/June 2024 · Q15 Marks
A random variable X has the distribution Po(145).
- (a)Use a suitable approximating distribution to calculate P(X≤ 150).[4]
- (b)Justify the use of your approximating distribution in this case.[1]
Mark scheme
Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.
- [B1] N(145, 145) Stated or implied.
- [M1] ± 150.5-145 / √145 Condone incorrect or omitted continuity correction.
- [M1] Φ('0.457') For area consistent with their working.
- [A1] = 0.676 (3sf) SC: Unsupported answer of 0.676 scores B3. Unsupported answer of 0.646 or 0.661 scores B2. Unsupported answer of 0.6799 scores B1.
- [B1] 145 > 15 Explicit. λ > 15 B0 if λ = 145 not stated. Accept > Accept mean for λ.
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