To find the interquartile range, you will list the data that is presented in the stem and leaf plot.
Find the median of the data (30.5)
Find the median of the lower half and the median of the upper half.
Subtract these two values.
The data are 20, 25, 30, 30, 31, 40, 41, 49.
27.5 40.5
40.5-27.5 = 13
The interquartile range is 13.