Apps. and Interpretation for IBDP Maths Ebook 1 | Page 243

69
Paper 1 – Effects of Coding in Data
Example
There are 20 items in a data set. The sum of the items is 100.
(a) Find the mean.
The variance of this data set is 2. Each value in the set is multiplied by 7.
(b) (i) Write down the value of the new mean.
(ii) Find the value of the new variance.
[2]
[3]
17
Solution
(a) The mean
100
�
20
(A1) for correct formula
� 5
A1 N2
(b) (i) 35 A1 N1
[2]
(ii)
The new variance
2
� (7 )(2)
(M1) for valid approach
� 98
A1 N2
[3]
Exercise 69
1. There are 15 items in a data set. The sum of the items is 150.
(a)
Find the mean.
The variance of this data set is 8. Each value in the set is multiplied by 3.
[2]
(b) (i) Write down the value of the new mean.
(ii)
Find the value of the new variance.
[3]
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