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Date November 2020 Marks available 3 Reference code 20N.2.SL.TZ0.S_2
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number S_2 Adapted from N/A

Question

Lucy sells hot chocolate drinks at her snack bar and has noticed that she sells more hot chocolates on cooler days. On six different days, she records the maximum daily temperature, T, measured in degrees centigrade, and the number of hot chocolates sold, H. The results are shown in the following table.

The relationship between H and T can be modelled by the regression line with equation H=aT+b.

Find the value of a and of b.

[3]
a.i.

Write down the correlation coefficient.

[1]
a.ii.

Using the regression equation, estimate the number of hot chocolates that Lucy will sell on a day when the maximum temperature is 12°C.

[2]
b.

Markscheme

valid approach       (M1)

eg    correct value for a or b (or for r or r2=0.962839 seen in (ii))

a=-9.84636, b=221.592

a=-9.85, b=222        A1A1   N3

[3 marks]

a.i.

-0.981244

r=-0.981        A1  N1

[1 mark]

a.ii.

correct substitution into their equation       (A1)

eg       -9.85×12+222

103.435  (103.8 from 3 sf)

103  (hot chocolates)        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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