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Date May 2019 Marks available 2 Reference code 19M.2.SL.TZ1.T_1
Level Standard Level Paper Paper 2 Time zone Time zone 1
Command term Find and Use Question number T_1 Adapted from N/A

Question

A healthy human body temperature is 37.0 °C. Eight people were medically examined and the difference in their body temperature (°C), from 37.0 °C, was recorded. Their heartbeat (beats per minute) was also recorded.

Write down, for this set of data the mean temperature difference from 37 °C, x ¯ .

[1]
b.i.

Write down, for this set of data the mean number of heartbeats per minute, y ¯ .

[1]
b.ii.

Plot and label the point M( x ¯ , y ¯ ) on the scatter diagram.

[2]
c.

Use your graphic display calculator to find the Pearson’s product–moment correlation coefficient, r .

[2]
d.i.

Hence describe the correlation between temperature difference from 37 °C and heartbeat.

[2]
d.ii.

Draw the regression line y on x on the scatter diagram.

[2]
f.

Markscheme

0.025  ( 1 40 )     (A1)

[1 mark]

b.i.

74        (A1)

[1 mark]

b.ii.

the point M labelled, correctly plotted on their diagram        (A1)(A1)(ft)

Note: Award (A1) for labelled M. Do not accept any other label. Award (A1)(ft) for their point M correctly plotted. Follow through from part (b).

[2 marks]

c.

0.807 (0.806797…)       (G2)

[2 marks]

d.i.

(moderately) strong, positive       (A1)(ft)(A1)(ft)

Note: Award (A1) for (moderately) strong, (A1) for positive. Follow through from part (d)(i). If there is no answer to part (d)(i), award at most (A0)(A1).

[2 marks]

d.ii.

their regression line correctly drawn on scatter diagram (A1)(ft)(A1)(ft)

Note: Award (A1)(ft) for a straight line, using a ruler, intercepting their mean point, and (A1)(ft) for intercepting the y -axis at their 73.5 and the gradient of the line is positive. If graph paper is not used, award at most (A1)(A0). Follow through from part (e).

[2 marks]

f.

Examiners report

[N/A]
b.i.
[N/A]
b.ii.
[N/A]
c.
[N/A]
d.i.
[N/A]
d.ii.
[N/A]
f.

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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