A-LevelMathematicsProbability and statistics9709/61 · May/June 2025 · Q13 Marks
It is known that 1% of houses in a certain area have a wind turbine. A random sample of 400 houses in this area is chosen for a survey on domestic heating. The number of houses in the sample that have a wind turbine is denoted by X.
- Use a suitable approximating distribution to find P(X≤ 3).[3]
Mark scheme
Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.
- [B1] (λ) = 4
- [M1] Allow any λ, allow one end error.
- [A1] SC1 Unsupported answer of 0.433 scores B1B1. SC2 Use of Normal mean = 4 B1. SC3 Use Binomial 0.432 or 0.433 scores B1.
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