| Date | November 2007 | Marks available | 2 | Reference code | 07N.1.sl.TZ0.14 |
| Level | SL only | Paper | 1 | Time zone | TZ0 |
| Command term | Find | Question number | 14 | Adapted from | N/A |
Question
Tania wishes to see whether there is any correlation between a person’s age and the number of objects on a tray which could be remembered after looking at them for a certain time.
She obtains the following table of results.
Use your graphic display calculator to find the equation of the regression line of y on x.
Use your equation to estimate the number of objects remembered by a person aged 28 years.
Use your graphic display calculator to find the correlation coefficient r.
Comment on your value for r.
Markscheme
\(a = -0.134, b = 20.9\) (A1)
\(y = 20.9 - 0.134x\) (A1) (C2)
[2 marks]
17 objects (A1)(ft)
accept only 17 (C1)
[1 mark]
\(r = -0.756\) (A1) (C1)
[1 mark]
negative and moderately strong (A1)(ft)(A1)(ft) (C2)
[2 marks]
Examiners report
This question expected the candidates to use their GDC to find the equation of the regression line and to find the correlation coefficient and this was stated in the question parts. However, there were a number of candidates from specific schools who had not been taught to do this and they tried to find the equation from the formula in the information booklet. This would have wasted time and they did not manage to find the correct answer. This was also the case for the correlation coefficient. However, most candidates who found a correlation coefficient managed to comment on it correctly.
This question expected the candidates to use their GDC to find the equation of the regression line and to find the correlation coefficient and this was stated in the question parts. However, there were a number of candidates from specific schools who had not been taught to do this and they tried to find the equation from the formula in the information booklet. This would have wasted time and they did not manage to find the correct answer. This was also the case for the correlation coefficient. However, most candidates who found a correlation coefficient managed to comment on it correctly.
Many candidates did not give a whole number answer for the number of objects in part (b).
This question expected the candidates to use their GDC to find the equation of the regression line and to find the correlation coefficient and this was stated in the question parts. However, there were a number of candidates from specific schools who had not been taught to do this and they tried to find the equation from the formula in the information booklet. This would have wasted time and they did not manage to find the correct answer. This was also the case for the correlation coefficient. However, most candidates who found a correlation coefficient managed to comment on it correctly.
This question expected the candidates to use their GDC to find the equation of the regression line and to find the correlation coefficient and this was stated in the question parts. However, there were a number of candidates from specific schools who had not been taught to do this and they tried to find the equation from the formula in the information booklet. This would have wasted time and they did not manage to find the correct answer. This was also the case for the correlation coefficient. However, most candidates who found a correlation coefficient managed to comment on it correctly.
