IQR

IQR(interquartile range)=Q1-Q3

• Top box (Q1) below this value are 75% all the data points.
• Median (Q2)
• interquartile range 50% of all the data point are within this range.
• Bottom box (Q3) above this value are 7% of all the data points

http://en.wikipedia.org/wiki/Boxplot