| Date | May 2018 | Marks available | 1 | Reference code | 18M.1.sl.TZ2.3 |
| Level | SL only | Paper | 1 | Time zone | TZ2 |
| Command term | Write down | Question number | 3 | Adapted from | N/A |
Question
A data set has n items. The sum of the items is 800 and the mean is 20.
The standard deviation of this data set is 3. Each value in the set is multiplied by 10.
Find n.
[2]
a.
Write down the value of the new mean.
[1]
b.i.
Find the value of the new variance.
[3]
b.ii.
Markscheme
correct approach (A1)
eg \(\frac{{800}}{n} = 20\)
40 A1 N2
[2 marks]
a.
200 A1 N1
[1 mark]
b.i.
METHOD 1
recognizing variance = σ 2 (M1)
eg 32 = 9
correct working to find new variance (A1)
eg σ 2 × 102, 9 × 100
900 A1 N3
METHOD 2
new standard deviation is 30 (A1)
recognizing variance = σ 2 (M1)
eg 32 = 9, 302
900 A1 N3
[3 marks]
b.ii.
Examiners report
[N/A]
a.
[N/A]
b.i.
[N/A]
b.ii.
