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2.4 N: Statistical distributions

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Question 80

A biologist plants 10 seeds in each of 200 trays and records how many germinate in each tray. She models the number germinating in a tray by the random variable XXX, where X∼B(10,0.7)X \sim B(10, 0.7)X∼B(10,0.7).

a.

Find the mean and the variance of XXX.

[2]
b.

Using the model, find the expected number of trays in which all 10 seeds germinate.

[2]
c.

In fact, all 10 seeds germinated in 22 of the 200 trays. Comment on the model in the light of this.

[2]
d.

Suggest one reason why a binomial model may not be appropriate for this situation.

[1]
Markscheme

2.4 N: Statistical distributions Questions

  1. A Level
  2. /Maths
  3. /2.4 N: Statistical distributions

390 exam-style questions on AQA A Level Maths 2.4 N: Statistical distributions, covering 2.4.1 Discrete distributions and the binomial, 2.4.2 The Normal distribution (A-level only), and 2.4.3 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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