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Date May 2019 Marks available 1 Reference code 19M.2.SL.TZ2.S_1
Level Standard Level Paper Paper 2 Time zone Time zone 2
Command term Find Question number S_1 Adapted from N/A

Question

A group of 7 adult men wanted to see if there was a relationship between their Body Mass Index (BMI) and their waist size. Their waist sizes, in centimetres, were recorded and their BMI calculated. The following table shows the results.

The relationship between x and y can be modelled by the regression equation y = a x + b .

Write down the value of a and of b .

[3]
a.i.

Find the correlation coefficient.

[1]
a.ii.

Use the regression equation to estimate the BMI of an adult man whose waist size is 95 cm.

[2]
b.

Markscheme

valid approach       (M1)

eg      correct value for a or b (or for correct r or r 2 = 0.955631 seen in (ii))

0.141120,  11.1424

a = 0.141,  b = 11.1     A1A1 N3

[3 marks]

a.i.

0.977563

r = 0.978     A1 N1

[1 mark]

a.ii.

correct substitution into their regression equation       (A1)

eg      0.141(95) + 11.1

24.5488

24.5       A1 N2

[2 marks]

b.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.4—Pearsons, scatter diagrams, eqn of y on x
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Topic 4—Statistics and probability

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