finding interquartile range from dot plot 1
Post on 16-Jul-2015
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- Mr Kim
Finding IQR for odd number of scores
0 1 2 3 4 5
0 1 2 3 4 5
Here is a Dot Plot
0 1 2 3 4 5
First, find the Median by crossing off the dots
0 1 2 3 4 5
Start by crossing off the Bottom dot from the
Smallest Score
0 1 2 3 4 5
Start by crossing off the Bottom dot from the
Smallest Score
0 1 2 3 4 5
0 1 2 3 4 5
Now cross off the Top dot from the Biggest Score
0 1 2 3 4 5
Now cross off the Top dot from the Biggest Score
0 1 2 3 4 5
0 1 2 3 4 5
Cross off the dots in the directions shown
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
Stop here
0 1 2 3 4 5
Always stop at “Out”
0 1 2 3 4 5
So the Median (Q2) is 3
0 1 2 3 4 5
Now divide the Dot Plot in two
0 1 2 3 4 5
**It is very important to divide the sides properly
0 1 2 3 4 5
To do this, count the dots from the start until you
reach the Median
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
Stop here!
0 1 2 3 4 5
Now put a Border around the dots that you just
counted
0 1 2 3 4 5
0 1 2 3 4 5
Now put a Border around the other side
0 1 2 3 4 5
0 1 2 3 4 5
This is how you correctly divide the sides
0 1 2 3 4 5
Notice there are 9 dots on each side
0 1 2 3 4 5
9 in here
0 1 2 3 4 5
And 9 in here
9 in here
0 1 2 3 4 5
This is the INCORRECT
0 1 2 3 4 5
There are 7 dots in here
There are 11 dots in here
This is the INCORRECT
0 1 2 3 4 5
0 1 2 3 4 5
Now find the Median for both sides of the dots
0 1 2 3 4 5
Start with this side
0 1 2 3 4 5
Remember the directions
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
“In”
0 1 2 3 4 5
“Out”
0 1 2 3 4 5
Stop here
0 1 2 3 4 5
So the Lower Quartile (Q1) is…
0 1 2 3 4 5
So the Lower Quartile (Q1) is1
0 1 2 3 4 5
Lower Quartile: 1
0 1 2 3 4 5
Lower Quartile: 1
Now do the same to the other side
0 1 2 3 4 5
Lower Quartile: 1
Remember the directions
0 1 2 3 4 5
Lower Quartile: 1
“In”
0 1 2 3 4 5
Lower Quartile: 1
“Out”
0 1 2 3 4 5
Lower Quartile: 1
“In”
0 1 2 3 4 5
Lower Quartile: 1
“Out”
0 1 2 3 4 5
Lower Quartile: 1
“In”
0 1 2 3 4 5
Lower Quartile: 1
“Out”
0 1 2 3 4 5
Lower Quartile: 1
“In”
0 1 2 3 4 5
Lower Quartile: 1
“Out”
0 1 2 3 4 5
Lower Quartile: 1
Stop here
0 1 2 3 4 5
Lower Quartile: 1
So the Upper Quartile (Q3)is …
0 1 2 3 4 5
Lower Quartile: 1
So the Upper Quartile (Q3)is 4
0 1 2 3 4 5
Lower Quartile: 1 Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:
Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:
Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:4 –
Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:4 –
Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:4 – 1
Upper Quartile: 4
0 1 2 3 4 5
Lower Quartile: 1
So the Interquartile Range is:4 – 1 = 3
Our Final Answer!
Upper Quartile: 4
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