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2.4 Statistical Distributions

2.4 Statistical Distributions

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Question 59

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.

State two conditions needed for the binomial model to be appropriate.

[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 Statistical Distributions Questions

  1. A Level
  2. /Maths
  3. /2.4 Statistical Distributions

390 exam-style questions on OCR A Level Maths 2.4 Statistical Distributions, covering 2.4.1 Discrete probability distributions, 2.4.2 Binomial distribution as a model, 2.4.3 Calculating binomial probabilities, 2.4.4 Mean and variance of the binomial (A-level only), 2.4.5 Normal distribution as a model (A-level only), 2.4.6 Probabilities using the normal distribution (A-level only), 2.4.7 Links to histograms, mean and standard deviation (A-level only), and 2.4.8 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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