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Date May 2021 Marks available 2 Reference code 21M.2.SL.TZ1.2
Level Standard Level Paper Paper 2 Time zone Time zone 1
Command term Predict Question number 2 Adapted from N/A

Question

The following table shows the data collected from an experiment.

The data is also represented on the following scatter diagram.

The relationship between x and y can be modelled by the regression line of y on x with equation y=ax+b, where a, b.

Write down the value of a and the value of b.

[2]
a.

Use this model to predict the value of y when x=18.

[2]
b.

Write down the value of x¯ and the value of y¯.

[1]
c.

Draw the line of best fit on the scatter diagram.

[2]
d.

Markscheme

a=0.433156, b=4.50265

a=0.433, b=4.50        A1A1

 

[2 marks]

a.

attempt to substitute x=18 into their equation        (M1)

y=0.433×18+4.50

=12.2994

=12.3        A1

 

[2 marks]

b.

x¯=15,  y¯=11        A1

 

[1 mark]

c.

        A1A1

Note: Award marks as follows:

A1 for a straight line going through 15,11

A1 for intercepting the y-axis between their b±1.5 (when their line is extended), which includes all the data for 3.3x25.3.

If the candidate does not use a ruler, award A0A1 where appropriate.

 

[2 marks]

d.

Examiners report

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

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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