Apps. and Interpretation for IBDP Maths Ebook 1 | Page 323

Exercise 91
1. The following table shows the final exam scores for given midterm test scores in a group
of students.
Midterm test scores ( x ) 80 83 86 89 92
Final exam scores ( y ) 70 71 67 63 77
(a)
The relationship between the variables is modelled by the regression equation
y �ax � b .
(i) Write down the value of a and of b .
(ii)
Hence, estimate the final exam score of a student whose midterm test
score is 85.
(b) (i) Write down the correlation coefficient.
[4]
(ii)
State which two of the following describe the correlation between the
variables.
positive strong zero
negative weak no correlation
[3]
2. The following table shows the temperature y degrees Celsius of a liquid, x hours after
the start of an experiment.
x 0 2 4 6 8 10
y 90 92 88 103 70 71
22
(a)
The relationship between the variables is modelled by the regression equation
y �ax � b .
(i) Write down the value of a and of b .
(ii)
Hence, estimate the temperature of the liquid 9 hours after the start of the
experiment.
[4]
313
www.seprodstore.com