What is the interquartile range of this set of data? 15, 19, 20, 25, 31, 38, 41 6 13 19 26

Arrange this data in ascending order:

{6, 13, 15, 19, 19, 20, 25, 26, 31 38, 41}

The median is the center item, which here is 20.
The median of the left half of the items, not incl. 20, is 15.  This is QI.
The median of the right half the items, not incl. 20, is 31.  This is QIII.

The IQR is the difference between QI and QIII and is 31-15, or 16 (answer)