Quartiles
Quartiles are values that divide a sample of data into four equal parts. They are commonly used to describe data sets.
First quartile (Q1)
25% of the data are less than or equal to this value.
Second quartile (Q2)
The median. 50% of the data are less than or equal to this value.
Third quartile (Q3)
75% of the data are less than or equal to this value.
For example, for the following data: 7, 9, 16, 36, 39, 45, 45, 46, 48, 51
· Q1 = 16
· Q2 (median) = 42
· Q3 = 46
The interquartile range is equal to the distance between the first and third quartiles (Q3-Q1); thus, it spans the middle 50% of the data.
2006-03-28 10:05