For example
First list the values in order:
3 4 5 7 9 10 18
(a) As there are 7 values, the median will be the 7 1
2
4 + = th value.
Median = 7.
(b) The lower quartile will be the 7 1
4
2 + = nd value.
Lower quartile = 4.
The upper quartile will be the 37 1
4
6 ( ) + = th value.
Upper quartile = 10.
The interquartile range = upper quartile – lower quartile
= 10 4 −
= 6
The semi-interquartile range = interquartile range
2
= 6
2
= 3
