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Quartiles
What is a Quartile?
Quartiles
are values that divide a set of data into four equal parts.
There are four different types of quartiles
~Lower Quartile(LQ)-Q1
~Median Quartile-Q2
~Upper Quartile(UQ)-Q3
~Interquartile range(IQR)
Working out each Quartile
Below there are some numbers , to work out the median quartile I
must
put these numbers in order.
2.9 ,3.3 ,3.7 3.4, 3.0 ,3.5 ,3.8 ,3.4 ,3.1 ,3.9 ,3.2,3.3, ,3.4 ,3.6 ,4.0 ,4.1 3.4
{not in order
2.9 ,3.0 ,3.1 ,3.2 ,3.3 ,3.3,3.4 ,3.4 ,3.4 ,3.4 ,3.5 ,3.6 ,3.7 ,3.8, 3.9, 4.0, 4.1
{in order
My second step is work out the median from the list that answer will be Q2.
2.9 ,3.0 ,3.1 ,3.2 ,3.3 ,3.3 ,3.4 ,3.4 ,3.4 ,3.4 ,3.5 ,3.6 ,3.7 ,3.8, 3.9, 4.0, 4.1
As I have 17 numbers I need the 9th number for the median which is 3.4
Q2=
3.4
The third step is to find the median from the number either side of 3.4
I have used the number 3.4 already and cannot reuse it so the remaining data is shown below:
2.9 ,3.0 ,3.1 ,3.2 ,3.3 ,3.3 ,3.4 ,3.4 and 3.4 ,3.5 ,3.6 ,
3.7 ,3.8
, 3.9, 4.0, 4.1
Q1=
3.25
(3.2+3.3/2)
Q3=
3.75
(3.7+3.8/2)
How to find the Interquartile range?(IQR)
The interquartile range is found by subtracting the lower quartile from the upper quartile.
In this case the upper quartile is 3.75 and the lower quartile is 3.25
therefore the sum is 3.75-3.25=0.5
0.5=The Interquartile Range
Answers:
Q1=3.25 Q2=3.4 Q3=3.75 IQR=0.5