Apps. and Interpretation for IBDP Maths Ebook 1 | Page 324

Your Practice Set – Applications and Interpretation for IBDP Mathematics
(b) (i) Write down the correlation coefficient.
(ii)
State which two of the following describe the correlation between the
variables.
positive strong zero
negative weak moderate
[3]
3. The following table shows the Mathematics test scores ( x ) and the Physics test scores ( y )
of 7 students.
Mathematics test scores ( x ) 14 19 16 20 30 17 11
Physics test scores ( y ) 16 19 18 23 30 16 19
(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 Physics test score of a student whose Mathematics test
score is 25.
[4]
A teacher believes that the relationship between the Mathematics test scores ( x ) and the
Chemistry test scores ( w ) of the students can be modelled by a linear regression equation.
(b)
The teacher describes the correlation as very strong and negative. Circle the
value below which best represents the correlation coefficient.
0.989 0.178 0 � 0.178
� 0.989
[1]
(c) The teacher’s model is w� �0.18x� 25.6 . Use his model to predict the difference
in Chemistry test scores of two students if the difference of their Mathematics test
scores is 3.
[2]
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