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Date May 2018 Marks available 2 Reference code 18M.2.SL.TZ2.S_1
Level Standard Level Paper Paper 2 Time zone Time zone 2
Command term Estimate Question number S_1 Adapted from N/A

Question

The following table shows the mean weight, y kg , of children who are x years old.

The relationship between the variables is modelled by the regression line with equation  y = a x + b .

Find the value of a and of b.

[3]
a.i.

Write down the correlation coefficient.

[1]
a.ii.

Use your equation to estimate the mean weight of a child that is 1.95 years old.

[2]
b.

Markscheme

valid approach      (M1)

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

a = 1.91966  b = 7.97717

a = 1.92,  b = 7.98      A1A1 N3

[3 marks]

a.i.

0.984674

= 0.985      A1 N1

[1 mark]

a.ii.

correct substitution into their equation      (A1)
eg  1.92 × 1.95 + 7.98

11.7205

11.7 (kg)      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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