Apps. and Interpretation for IBDP Maths Ebook 1 | Page 229

SUMMARY POINTs
� Measures of dispersion for a data set { x1 , x2, x3, , x } arranged in ascending
order:
1. xn
� x1
: Range
2. Two subgroups A and B can be formed from the data set such that all
data of the subgroup A are less than or equal to the median, while all
data of the subgroup B are greater than or equal to the median
3. Q1
� The median of the subgroup A: Lower quartile
4. Q3
� The median of the subgroup B: Upper quartile
5. Q3�
Q1
6.
� �
: Inter-quartile range (IQR)
( x � x) � ( x � x) � ( x � x) � � ( x � x)
n
2 2 2 2
1 2 3
n
n
: Standard deviation
17
�
Box-and-whisker diagram:
� A datum x is defined to be an outlier if x�Q1 � 1.5IQR or x�Q3 � 1.5IQR
Coding of data:
1. Only the mean, the median, the mode and the quartiles will change
when each datum of the data set is added or subtracted by a value
2. All measures of central tendency and measures of dispersion will
change when each datum of the data set is multiplied or divided by a
value
Solutions of Chapter 17
www.seprodstore.com
219