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Date May Example question Marks available 10 Reference code EXM.2.AHL.TZ0.29
Level Additional Higher Level Paper Paper 2 Time zone Time zone 0
Command term Test and State Question number 29 Adapted from N/A

Question

A horse breeder records the number of births for each of 100 horses during the past eight years. The results are summarized in the following table:

Stating null and alternative hypotheses carry out an appropriate test at the 5% significance level to decide whether the results can be modelled by B (6, 0.5).

[10]
a.

Without doing any further calculations, explain briefly how you would carry out a test, at the 5% significance level, to decide if the data can be modelled by B(6, p ), where p  is unspecified.

[2]
b.

A different horse breeder collected data on the time and outcome of births. The data are summarized in the following table:

Carry out an appropriate test at the 5% significance level to decide whether there is an association between time and outcome.

[8]
c.

Markscheme

METHOD 1

H0: distribution is B(6, 0.5); H1: distribution is not B(6, 0.5)      A1

( E 0 = 100 ( 0.5 ) 6 = 25 16 = 0.015625 )       A3

Combining the first two columns and the last two columns:       A1

χ 2 = O 2 E E

= 6 2 ( 175 16 ) + 26 2 ( 375 16 ) + 37 2 ( 500 16 ) + 18 2 ( 375 16 ) + 13 2 ( 175 16 ) 100         (M1)

= 5.22       A1

v = 4, so critical value of χ 5 2 = 9.488        A1A1

Since 5.22 < 9.488 the result is not significant and we accept H0       R1

 

METHOD 2

H0: distribution is B(6, 0.5); H1: distribution is not B(6, 0.5)      A1

By GDC, p = 0.266       A8

Since 0.266 > 0.05 the result is not significant and we accept H0       R1

 

[10 marks]

a.

Estimate p  from the data which would entail the loss of one degree of freedom      A1A1

[2 marks]

b.

H0: there is no association H1: there is an association       A1

       A2

χ 2 = 68 2 64.8 + 42 2 45.2 + 103 2 94.3 + + 6 2 10.6 + 12 2 7.4 314         (M1)

     = 15.7

v = 3 , χ 5 2 ( 3 ) = 7.815        A1A1

Since 15.7 > 7.815 we reject H0           R1

 

METHOD 2

H0: there is no association H1: there is an association       A1

By GDC, p = 0.00129         A6

Since 0.00129 < 0.05 we reject H0.           R1

 

[8 marks]

c.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.11—Expected, observed, hypotheses, chi squared, gof, t-test
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Topic 4—Statistics and probability » AHL 4.12—Data collection, reliability and validity tests
Topic 4—Statistics and probability

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