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Date November 2021 Marks available 2 Reference code 21N.1.AHL.TZ0.12
Level Additional Higher Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number 12 Adapted from N/A

Question

The following table shows the time, in days, from December 1st and the percentage of Christmas trees in stock at a shop on the beginning of that day.

The following table shows the natural logarithm of both d and x on these days to 2 decimal places.

Use the data in the second table to find the value of m and the value of b for the regression line, lnx=m(lnd)+b.

 

[2]
a.

Assuming that the model found in part (a) remains valid, estimate the percentage of trees in stock when d=25.

[3]
b.

Markscheme

m=-0.695  -0.695383; b=4.63  4.62974                  A1A1

 

[2 marks]

a.

lnx=-0.695ln25+4.63                  M1

lnx=2.39288                  (A1)

x=10.9%                  A1

 

[3 marks]

b.

Examiners report

Those candidates who did this question were often successful. There were a number, however, who found an equation of a line through two of the points instead of using their technology to find the equation of the regression line. A common problem was to introduce rounding errors at various stages throughout the problem. Some candidates failed to find the value of x from that of ln x.

a.

Those candidates who did this question were often successful. There were a number, however, who found an equation of a line through two of the points instead of using their technology to find the equation of the regression line. A common problem was to introduce rounding errors at various stages throughout the problem. Some candidates failed to find the value of x from that of ln x.

b.

Syllabus sections

Topic 4—Statistics and probability » SL 4.4—Pearsons, scatter diagrams, eqn of y on x
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