Kwan recorded two sets of data.

Set 1: 9, 13, 6, 18, 15, 19, 20
Median: 15
Lower Quartile: 9
Upper Quartile: 19
Range: 14
IQR: 10

Set 2: 9, 13, 6, 18, 15, 19, 20, 63
Median: 16.5
Lower Quartile: 11
Upper Quartile: 19.5
Range: 57
IQR: 8.5

One set of data shows an outlier. Which measure of spread was most impacted by the outlier?
lower quartile
median
interquartile range (IQR)
range