We need to put the data set in ascending order
1.2 4.3 5.0 5.8 6.2 6.3 7.2 7.4 8.4
Interquartile range is given by upper quartile - lower quartile
Location of lower quartile = 1/4 of the data set
Location of upper quartile = 3/4 of the data set
Lower quartile = 1/4 of 9 = 2.25th (rounded down to 2nd value) = 4.3
Upper quartile = 3/4 of 9 = 6.75th (rounded up to 7th value) = 7.2
Interquartile value = 7.2 - 4.3 = 2.9
