Interquartile range

Problem:



Solution:

To find the interquartile range, you first sort the data

600 800 1000 1000

Assuming we are using the linear interpolation method documented in this website
https://en.wikipedia.org/wiki/Percentile 

Next, you find the 25 percentile value, which is 700 in this case.

 Next, you find the 75 percentile value, which is 1000 in this case.

Finally, you subtract them and get 300, that is the interquartile range.