What is the interquartile range?

Answer 1

Like the standard deviation, the interquartile range (IQR) is a descriptive statistic used to summarize the extent of the spread of your data. The IQR is the distance between the 1st quartile (25th percentile) and 3rd quartile (75th percentile).

Q3 - Q1 = IQR

To find these numbers you must divide your data set in half, and find the median of each half and that will be your Q1 and Q3.

If you have an odd number, then EXCLUDE the median of the entire set, so as follows:

For example, take the following dataset:

3 5 7 8 9 21 40 90 120

We exclude the 9 as the median of the whole set and the 1st quartile is 6 (5+7 divided by 2) and the 3rd quartile is 65 (40+90 divided by 2), making the IQR = 65-6=59.

OR

If you have this set:

3 5 7 8 40 90 120

We exclude the 8 as the median of the whole set and the 1st quartile is 5 and the 3rd quartile is 90. (90 - 5 = 85.)

Answer 2

9,5,14,6,8,9,6,2,3,5