12 . The following table shows the age of a car x ( in years ) and the corresponding number of oil refill .
Age of a car ( x years ) 1 2 3 4 5 Number of oil refill ( y ) 45 82 135 150 171
( 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 number of oil refills of a car when its age is 2.5 years .
[ 4 ]
( b ) ( i ) Write down the correlation coefficient .
( ii ) Write down the coefficient of determination .
( iii ) Hence , interpret the coefficient of determination . [ 3 ]
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