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Date November 2015 Marks available 2 Reference code 15N.2.hl.TZ0.8
Level HL only Paper 2 Time zone TZ0
Command term Find Question number 8 Adapted from N/A

Question

The continuous random variable X has the probability distribution function f(x)=Asin(ln(x)), 1x5.

Find the value of A to three decimal places.

[2]
a.

Find the mode of X.

[2]
b.

Find the value P(X3|X2).

[2]
c.

Markscheme

A51sin(lnx)dx=1     (M1)

A=0.323 (3 dp only)     A1

[2 marks]

a.

either a graphical approach or f(x)=cos(lnx)x=0     (M1)

x=4.81(=eπ2)     A1

 

Note:     Do not award A1FT for a candidate working in degrees.

[2 marks]

b.

P(X3|X2)=P(2X3)P(X2)(=32sin(ln(x))dx52sin(ln(x))dx)     (M1)

=0.288     A1

 

Note:     Do not award A1FT for a candidate working in degrees.

[2 marks]

Total [6 marks]

c.

Examiners report

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

Syllabus sections

Topic 5 - Core: Statistics and probability » 5.4 » Conditional probability; the definition P(A|P)=P(AB)P(B) .

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