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Date November 2016 Marks available 2 Reference code 16N.1.SL.TZ0.S_5
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number S_5 Adapted from N/A

Question

Events A and B are independent with P ( A B ) = 0.2 and P ( A B ) = 0.6 .

Find P ( B ) .

[2]
a.

Find P ( A B ) .

[4]
b.

Markscheme

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

valid interpretation (may be seen on a Venn diagram)     (M1)

eg P ( A B ) + P ( A B ) ,   0.2 + 0.6

P ( B ) = 0.8      A1     N2

[2 marks]

a.

valid attempt to find P ( A )      (M1)

eg P ( A B ) = P ( A ) × P ( B ) ,   0.8 × A = 0.2

correct working for P ( A )      (A1)

eg 0.25 ,   0.2 0.8

correct working for P ( A B )      (A1)

eg 0.25 + 0.8 0.2 ,   0.6 + 0.2 + 0.05

P ( A B ) = 0.85      A1     N3

[4 marks]

b.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.5—Probability concepts, expected numbers
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Topic 4—Statistics and probability » SL 4.6—Combined, mutually exclusive, conditional, independence, prob diagrams
Topic 4—Statistics and probability

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