What is the interquartile range of the data set? {18, 17, 10, 25, 20, 20, 30, 18, 18, 30, 25}

{18, 17, 10, 25, 20, 20, 30, 18, 18, 30, 25}

put in order

10, 17, 18, 18, 18,  20,  20, 25, 25, 30, 30
so 
median = 20
Lower IQR = (10+17+18+18+18)/5 = 81/5 = 16.2
Upper IQR = (20+25+25+30+30)/5 = 130/5 = 26

interquartile range = 26 - 16.2 = 9.8

answer 
interquartile range = 9.8