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2.4.4 Mean and variance of the binomial (A-level only)

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Question 25

A botanist observes that the number of seeds, SSS, that germinate in a large nursery plot follows a binomial distribution S∼B(n,p)S \sim \text{B}(n, p)S∼B(n,p). The expected number of germinated seeds is 200.

a.

State the variance of SSS in terms of ppp.

[1]
b.

A normal distribution is used as an approximation for SSS. Using this approximation and a continuity correction, the probability that 180 or fewer seeds germinate is approximately 0.0384.

Show that 200−200p=11.02\sqrt{200 - 200p} = 11.02200−200p​=11.02 to 4 significant figures.

[5]
c.

Hence find the value of ppp, giving your answer to 2 significant figures.

[3]

2.4.4 Mean and variance of the binomial (A-level only) Questions

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