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Date May 2017 Marks available 2 Reference code 17M.1.SL.TZ2.S_3
Level Standard Level Paper Paper 1 Time zone Time zone 2
Command term Find Question number S_3 Adapted from N/A

Question

The random variable X is normally distributed with a mean of 100. The following diagram shows the normal curve for X.

M17/5/MATME/SP1/ENG/TZ2/03

Let R be the shaded region under the curve, to the right of 107. The area of R is 0.24.

Write down P(X>107).

[1]
a.

Find P(100<X<107).

[3]
b.

Find P(93<X<107).

[2]
c.

Markscheme

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

P(X>107)=0.24(=625, 24%)     A1     N1

[1 mark]

a.

valid approach     (M1)

egP(X>100)=0.5, P(X>100)P(X>107)

correct working     (A1)

eg0.50.24, 0.760.5

P(100<X<107)=0.26(=1350, 26%)     A1     N2

[3 marks]

b.

valid approach     (M1)

eg2×0.26, 12(0.24), P(93<X<100)=P(100<X<107)

P(93<X<107)=0.52(=1325, 52%)     A1 N2

[2 marks]

c.

Examiners report

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

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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