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Date November 2021 Marks available 1 Reference code 21N.1.SL.TZ0.1
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Comment Question number 1 Adapted from N/A

Question

Eduardo believes that there is a linear relationship between the age of a male runner and the time it takes them to run 5000 metres.

To test this, he recorded the age, x years, and the time, t minutes, for eight males in a single 5000m race. His results are presented in the following table and scatter diagram.

Eduardo looked in a sports science text book. He found that the following information about r was appropriate for athletic performance.

For this data, find the value of the Pearson’s product-moment correlation coefficient, r.

[2]
a.

Comment on your answer to part (a), using the information that Eduardo found.

[1]
b.

Write down the equation of the regression line of t on x, in the form t=ax+b.

[1]
c.

A 57-year-old male also ran in the 5000m race.

Use the equation of the regression line to estimate the time he took to complete the 5000m race.

[2]
d.

Markscheme

r=0.933  0.933419              A2

 

[2 marks]

a.

strong             A1


Note: Answer may include “positive”, however this is not necessary for the mark.

 

[1 mark]

b.

t=0.228x+24.3   t=0.227703x+24.3153            A1


Note: Condone y in place of t. Answer must be an equation.

 

[1 mark]

c.

t=  0.227703×57+24.3153             (M1)


Note: Award (M1) for correct substitution into their regression line.


t=  37.3 minutes  37.2944        A1


Note: Accept 37.1 and 37.4 from use of 2sf and/or 3sf values.


[2 marks]

d.

Examiners report

Generally, a good starting point for most candidates. Most of them could find the correlation coefficient with a correct interpretation. They could find the regression equation and use it appropriately to make a prediction. It was observed that candidates used a mixture of two and three significant figures to reach an answer. Marks were generally awarded for their correct three significant answers or answers given to a higher degree of accuracy. The weaker candidates substituted 5000m instead of 57 years into their equation.

a.

Generally, a good starting point for most candidates. Most of them could find the correlation coefficient with a correct interpretation. They could find the regression equation and use it appropriately to make a prediction. It was observed that candidates used a mixture of two and three significant figures to reach an answer. Marks were generally awarded for their correct three significant answers or answers given to a higher degree of accuracy. The weaker candidates substituted 5000m instead of 57 years into their equation.

b.

Generally, a good starting point for most candidates. Most of them could find the correlation coefficient with a correct interpretation. They could find the regression equation and use it appropriately to make a prediction. It was observed that candidates used a mixture of two and three significant figures to reach an answer. Marks were generally awarded for their correct three significant answers or answers given to a higher degree of accuracy. The weaker candidates substituted 5000m instead of 57 years into their equation.

c.

Generally, a good starting point for most candidates. Most of them could find the correlation coefficient with a correct interpretation. They could find the regression equation and use it appropriately to make a prediction. It was observed that candidates used a mixture of two and three significant figures to reach an answer. Marks were generally awarded for their correct three significant answers or answers given to a higher degree of accuracy. The weaker candidates substituted 5000m instead of 57 years into their equation.

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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