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9 11:13

5.9
4.4

4.0
5.8

5.7
5.1

5.1
6.1

4.1
4.5

4.4
4.9

6.5
4.9

Fourteen Colorado counties were surveyed to see what percentage of children under 18 were living with their grandparents. The results are shown here.
What is the interquartile range of the data?

X

A

1.4

B

1.9

1×

C

2.1

D

2.4

×

Answer 1

First sort the 14 values:
4.0, 4.1, 4.4, 4.4, 4.5, 4.9, 4.9, 5.1, 5.1, 5.7, 5.8, 5.9, 6.1, 6.5

Median is average of 7th and 8th values: (4.9+5.1)/2 = 5.0.
Lower half (first 7): 4.0, 4.1, 4.4, 4.4, 4.5, 4.9, 4.9 → Q1 = 4.4
Upper half (last 7): 5.1, 5.1, 5.7, 5.8, 5.9, 6.1, 6.5 → Q3 = 5.8

IQR = Q3 − Q1 = 5.8 − 4.4 = 1.4

Answer: A (1.4).