Bryan is asked to find the interquartile range for the data set {5,6,6,8,10,11,14,16,17}. His work follows.
Step A: Find the median of the data set. The median, or Q2, is 10.

Step B: Find the value of Q1, or the median of the lower half of the data set, {5,6,6,8}. Q1=6+62=6

Step C: Find the value of Q3, or the median of the upper half of the data set, {11,14,16,17}. Q3=14+162=15

Step D: Find the difference between Q3 and Q1. IQR=15−6=9 At which step did Bryan make a mistake, if he made one?

He did not make a mistake.
A.) At Step A, he incorrectly found the value of the median. He should not have included both 6 values, so the median is 10+112=10.5.
B.) At Step B, he incorrectly found the value of Q1. He should have found the sum
of the values and then divided by 4 to get Q1=6.25.
C.) At Step D, he incorrectly found the IQR. He should have found the difference between each quartile to get 10−6=4 and 15−10=5.
D.) At Step C, he incorrectly found the value of Q3. He should have included 10 to get Q3=14.