What is the IQR of 64, 68, 70, 71, 72?

IQR is the difference between Q3 and Q1

64, 68, 70, 71, 72

Q2 = 70

Q1 is the median of the lower half. That will be the average of 64 & 68.

(64+68) / 2 = 66

Q3 is the median of the upper half. That will be the average of 71 & 72.

(71+72) / 2 = 71.5

IQR = 71.5-66 = 5.5

It's 8 because its 72 minus 64.