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Date May 2018 Marks available 3 Reference code 18M.2.AHL.TZ1.H_4
Level Additional Higher Level Paper Paper 2 Time zone Time zone 1
Command term Find Question number H_4 Adapted from N/A

Question

The age, L, in years, of a wolf can be modelled by the normal distribution L ~ N(8, 5).

Find the probability that a wolf selected at random is at least 5 years old.

[2]
a.

Eight wolves are independently selected at random and their ages recorded.

Find the probability that more than six of these wolves are at least 5 years old.

[3]
b.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

P(L ≥ 5) = 0.910      (M1)A1

[2 marks]

a.

X is the number of wolves found to be at least 5 years old recognising binomial distribution      M1

X ~ B(8, 0.910…)

P(X > 6) = 1 − P(X ≤ 6)      (M1)

= 0.843       A1

Note: Award M1A0 for finding P(X ≥ 6).

[3 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 4—Statistics and probability » SL 4.9—Normal distribution and calculations
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Topic 4—Statistics and probability

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