Write down the correlation coefficient, \(r\) , for the examination scores.

Write down the equation of the regression line, \(y\) on \(x\) , for the examination scores of the five candidates.

A sixth candidate scored 72 in the Mathematics examination. Use the regression line, \(y\) on \(x\), to estimate his score on the Physics examination.

\(r = 0.814\) \((0.813745...)\)     (A2)     (C2)

[2 marks]

\(y = 0.888x + 13.5\)     \((y = 0.887686 \ldots x + 13.4895 \ldots )\)     (A1)(A1)

Note: Award (A1) for \(0.888x\), (A1) for \(13.5\). If the answer is not in the form of an equation award (A1)(A0).

OR

\(y - 63.2 = 0.888(x - 56)\)     (A1)(A1)     (C2)

Note: Award (A1) for \(0.888\), (A1) for the correct means, \(\bar x\) and \(\bar y\) used.

[2 marks]

\(y = 0.887686 \ldots (72) + 13.4895 \ldots \)     (M1)

Note: Award (M1) for 72 substituted into their equation of the regression line.

\( = 77\)     \((77.4028…)\)     (A1)(ft)     (C2)

Note: Accept a correct (ft) integer value or a decimal value which would round to the required 3 sf answer (ft). Follow through from their equation in part (b).

[2 marks]

Able candidates scored very well on this question showing good use of their GDC and marks in excess of 4 were achieved by a large majority of these candidates. It was clear however, from some responses, that either the topic had not been taught or had been poorly understood by candidates and few, if any, marks were achieved by such candidates.

Able candidates scored very well on this question showing good use of their GDC and marks in excess of 4 were achieved by a large majority of these candidates. It was clear however, from some responses, that either the topic had not been taught or had been poorly understood by candidates and few, if any, marks were achieved by such candidates. In part (b), many candidates quoted a correct regression line equation using \(\bar x,\bar y,{s_{xy}}\) and \({s_{{x^2}}}\) but then seemed to be at a loss as to what to do with it.

Able candidates scored very well on this question showing good use of their GDC and marks in excess of 4 were achieved by a large majority of these candidates. It was clear however, from some responses, that either the topic had not been taught or had been poorly understood by candidates and few, if any, marks were achieved by such candidates. In part (b), many candidates quoted a correct regression line equation using \(\bar x,\bar y,{s_{xy}}\) and \({s_{{x^2}}}\) but then seemed to be at a loss as to what to do with it.