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Date May 2019 Marks available 2 Reference code 19M.2.AHL.TZ2.H_2
Level Additional Higher Level Paper Paper 2 Time zone Time zone 2
Command term Calculate Question number H_2 Adapted from N/A

Question

Timmy owns a shop. His daily income from selling his goods can be modelled as a normal distribution, with a mean daily income of $820, and a standard deviation of $230. To make a profit, Timmy’s daily income needs to be greater than $1000.

Calculate the probability that, on a randomly selected day, Timmy makes a profit.

[2]
a.

The shop is open for 24 days every month.

Calculate the probability that, in a randomly selected month, Timmy makes a profit on between 5 and 10 days (inclusive).

[3]
b.

Markscheme

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

X ~ N(820, 2302)       (M1)

Note: Award M1 for an attempt to use normal distribution. Accept labelled normal graph.

⇒P(X > 1000) = 0.217       A1

[2 marks]

a.

Y ~ B(24,0.217...)       (M1)

Note: Award M1 for recognition of binomial distribution with parameters.

P(Y ≤ 10) − P(Y ≤ 4)         (M1)

Note: Award M1 for an attempt to find P(5 ≤ Y ≤ 10) or P(Y ≤ 10) − P(Y ≤ 4).

= 0.613       A1

[3 marks]

b.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.8—Binomial distribution
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Topic 4—Statistics and probability » SL 4.9—Normal distribution and calculations
Topic 4—Statistics and probability

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