Answer:
7.5
Step-by-step explanation:
5, 8, 9, 11, 13, 15, 16, 17, 17, 18, 22, 23
Median: 15.5
(Q1) lower quartile: 10
(Q2) upper quartile: 17.5
interquartile range: 17.5 - 10 = 7.5
