� 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: Inter-quartile range ( IQR ) n
6 . |
� � |
|
( x
� x)
|
�
( x
|
� x) |
�
( x
� x)
|
� |
�
( x
|
� x) |
|
|
|
n |
|
|
|
2 2 2 2 1 2 3 n
|
: Standard deviation |
� 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
www . seprodstore . com
29