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Date May Example question Marks available 2 Reference code EXM.1.SL.TZ0.11
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Explain Question number 11 Adapted from N/A

Question

A calculator generates a random sequence of digits. A sample of 200 digits is randomly selected from the first 100 000 digits of the sequence. The following table gives the number of times each digit occurs in this sample.

It is claimed that all digits have the same probability of appearing in the sequence.

Test this claim at the 5% level of significance.

[7]
a.

Explain what is meant by the 5% level of significance.

[2]
b.

Markscheme

H0: The sequence contains equal numbers of each digit.       (A1)

H1: The sequence does not contain equal numbers of each digit.      (A1)

χ calc 2 = ( 9 + 1 + 25 + 1 + 25 + 49 + 1 + 9 + 4 + 16 ) 20 = 7        (M1)(A1)

The number of degrees of freedom is 9.        (A1)

χ 0.95 ; 5 2 = 16.919         (A1)

χ calc 2 < 16.919 . Hence H0 is accepted.        (A1)

[7 marks]

a.

The probability of rejecting H0 when it is true          (A1)

is 0.05.          (A1)

Note:  Award (A1)(A1) for “the probability of a type I error is 0.05.”

[2 marks]

b.

Examiners report

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

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

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