1. ©G Dear 2008 – Not to be sold/Free to use
General Mathematics
Preliminary
Displaying
Data
Interquartile
Range
Stage 6 - Year 11
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©G Dear 2008 – Not to be sold/Free to use

2. Interquartile Range
The difference between the upper quartile and the lower quartile.
The quartiles are found by dividing the ordered data in half and then quarters.
The IQR measures the middle 50% of scores
2, 4, 4, 5, 6, 7, 7.
Median = 5 Q1
Lower Quartile
Upper Quartile Q3
IQR =
Q3 - Q1 =
7 - 4 = 3

3. 2, 3, 5, 5, 7, 7, 9, 9. Interquartile Range (Data must be in order)
3+5 2
5+7 2
7+9 2
Q1 =
Median =
Q3 =
= 4
= 6
= 8
IQR =
Q3 - Q1 =
8 - 4 = 4

4. Interquartile Range IQR = Q3 - Q1 = 3.2 - 1.3 = 1.9 % cf x 100% 75%1 2 3 4 5 10 15 20 25 30 cf x
100%
75%
50%
25% 0%
Q1=1.3
Median=2.1
Q3=3.2
IQR =
Q3 - Q1 = =
1.9