Analysis and Approaches for IBDP Maths Ebook 1 | Page 303

Front Page
Exercise 98
1. The following table shows the public exam score x and university entrance mark y for
five students.
Public exam score ( x ) 172 178 185 190 191
University entrance mark ( y ) 21.2 22.4 22.5 24.5 24.1
This data can be modelled by the regression line with equation y �ax � b .
(a) (i) Write down the value of a and of b .
(b)
(ii)
Explain what the gradient a represents.
Sarah scored a total of 180 in her public exam. Use the model to estimate her
university entrance mark.
[3]
[2]
2. The following table shows the sales, y millions of dollars, of an online shop, x years
after 2011.
Number of years after 2011
( x years)
1 2 3 4 5 6
Sales ( y millions of dollars) 6.8 7.7 9.9 13.7 21.2 21.9
The relationship between the variables modelled by the regression line with equation
y �ax � b .
(a) (i) Find the value of a and of b .
(ii)
Explain what the intercept b represents.
(b) Hence estimate the sales in millions of dollars thirty months after 2011.
[3]
[2]
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www.seprodstore.com
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