OG里的一个例子:
Example 4.2.6: In the list of 16 numbers 2, 4, 4, 5, 7, 7, 7, 7, 7, 7, 8, 8, 9, 9, 9, 9, the range is 9−2=7, the first quartile is Q1 =6, and the third quartile is Q3 =8.5. So the interquartile range for the numbers in this list is 8.5 − 6 = 2.5.
Because the number of data in a list may not be divisible by 4, there are various rules to determine the exact values of Q1 and Q3 and some statisticians use different rules, but in all cases Q2 = M. We use perhaps the most common rule, in which Q2 = M divides the data into two equal parts — the lesser numbers and the greater numbers—and then Q1 is the median of the lesser numbers and Q3 is the median of the greater numbers