| Date | May 2018 | Marks available | 2 | Reference code | 18M.2.sl.TZ2.1 |
| Level | SL only | Paper | 2 | Time zone | TZ2 |
| Command term | Estimate | Question number | 1 | Adapted from | N/A |
Question
The following table shows the mean weight, y kg , of children who are x years old.
The relationship between the variables is modelled by the regression line with equation \(y = ax + b\).
Find the value of a and of b.
[3]
a.i.
Write down the correlation coefficient.
[1]
a.ii.
Use your equation to estimate the mean weight of a child that is 1.95 years old.
[2]
b.
Markscheme
valid approach (M1)
eg correct value for a or b (or for r seen in (ii))
a = 1.91966 b = 7.97717
a = 1.92, b = 7.98 A1A1 N3
[3 marks]
a.i.
0.984674
r = 0.985 A1 N1
[1 mark]
a.ii.
correct substitution into their equation (A1)
eg 1.92 × 1.95 + 7.98
11.7205
11.7 (kg) A1 N2
[2 marks]
b.
Examiners report
[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.
