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Date May 2018 Marks available 1 Reference code 18M.1.sl.TZ2.3
Level SL only Paper 1 Time zone TZ2
Command term Write down Question number 3 Adapted from N/A

Question

A data set has n items. The sum of the items is 800 and the mean is 20.

The standard deviation of this data set is 3. Each value in the set is multiplied by 10.

Find n.

[2]
a.

Write down the value of the new mean.

[1]
b.i.

Find the value of the new variance.

[3]
b.ii.

Markscheme

correct approach      (A1)

eg  \(\frac{{800}}{n} = 20\)

40      A1 N2

[2 marks]

a.

200   A1 N1

[1 mark]

b.i.

METHOD 1

recognizing variance = σ 2      (M1)

eg  32 = 9

correct working to find new variance      (A1)

eg  σ × 102, 9 × 100

900      A1 N3

 

METHOD 2

new standard deviation is 30      (A1)

recognizing variance = σ 2      (M1)

eg 32 = 9, 302

900      A1 N3

[3 marks]

b.ii.

Examiners report

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

Syllabus sections

Topic 5 - Statistics and probability » 5.2 » Statistical measures and their interpretations.
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