Before we can find the range, and interquartile range let's review the definitions of these terms.
Range: the difference between the greatest and least values.
Interquartile Range: the difference between the first quartile and third quartile.
First, we will write the data in numerical order.
26, 28, 29, 30, 30, 31
Range
The range is the difference between the greatest and least values.
26, 28, 29, 30, 30, 31
The difference between 31 and 26 is 5.
Interquartile Range
To find the interquartile range, we need to find the median of the lower half, the first quartile, and the median of the upper half, the third quartile.
Median_L Median_U
↓ ↓
26,28,29 30, 30, 31
Lower Half Upper Half
The first quartile is 28 and the third quartile is 30. The difference between the two values is 30-28=2.
Therefore, the interquartile range is 2.
