The document explains how to find the interquartile range (IQR) from a set of even-numbered scores using a dot plot. It outlines the steps for determining the median, lower quartile (Q1), upper quartile (Q3), and subsequently calculating the IQR. The final calculated IQR is 1.5.

1. - Mr Kim

2. Finding IQR for even number of scores

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Here is a Dot Plot

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First, find the Median by
crossing off the dots

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Start by crossing off the
Bottom dot from the
Smallest Score

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Start by crossing off the
Bottom dot from the
Smallest Score

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Now cross off the Top dot
from the Biggest Score

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Now cross off the Top dot
from the Biggest Score

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Cross off the dots in
the directions shown

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Notice there are no dots
above 2, so skip to the next
dot

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Notice there are no dots
above 2, so skip to the next
dot

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“In”

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“Out”

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“In”

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“Out”

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“In”

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“Out”

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“In”

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“Out”

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“In”

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“Out”

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“In”

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“Out”

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Stop here

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Always stop at “Out”

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Now, put a line between
the two dots

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Now, put a line between
the two dots

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The Median is between
those two dots

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This dot is…

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This dot is 6

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This dot is…

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This dot is also 6

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So the Median (Q2) is
between 6 and 6 which is
…

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So the Median (Q2) is
between 6 and 6 which is
6

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Now divide the Dot Plot
in two

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**It is very important to
divide the sides properly

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To do this, count the dots
from the start until you
reach the line

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Stop here

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Now put a Border around
the dots that you just
counted

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Now put a Border around
the other side

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This is how you correctly
divide the sides

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Notice there are
8 dots on each side

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8 in here

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8 in here
And 8 in here

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This is the INCORRECT

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Do you notice
the difference?
This is the INCORRECT

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This is the INCORRECT
There are 9 in
here
And 7 in here

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Now find the Median for
both sides of the dots

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Start with this side

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Remember the
directions

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“In”

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“Out”

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“In”

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“Out”

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“In”

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“Out”

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Stop here

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The Lower Quartile (Q1)
is between the two dots

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The Lower Quartile (Q1)
is between the two dots

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The 4

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And the 5

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So the Lower Quartile (Q1) is
between 4 and 5 which is…

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So the Lower Quartile (Q1) is
between 4 and 5 which is 4.5

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Lower Quartile:
4.5

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Lower Quartile:
4.5
Now cross off the other
side

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Lower Quartile:
4.5
Remember the
directions

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Lower Quartile:
4.5
“In”

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Lower Quartile:
4.5
“Out”

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Lower Quartile:
4.5
“In”

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Lower Quartile:
4.5
“Out”

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Lower Quartile:
4.5
“In”

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Lower Quartile:
4.5
“Out”

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Lower Quartile:
4.5
Stop here

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Lower Quartile:
4.5
The Upper Quartile (Q3)
is between the two dots

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Lower Quartile:
4.5
The Upper Quartile (Q3)
is between the two dots

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Lower Quartile:
4.5
Both of these dots
belong to the score…

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Lower Quartile:
4.5
Both of these dots
belong to the score 6

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Lower Quartile:
4.5
So the Upper Quartile (Q3) is
between 6 and 6 which is…

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Lower Quartile:
4.5
So the Upper Quartile (Q3) is
between 6 and 6 which is 6

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Lower Quartile:
4.5
Upper Quartile: 6

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:
6 -

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:
6 -

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:
6 – 4.5

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Lower Quartile:
4.5
Upper Quartile: 6
So the Interquartile Range is:
6 – 4.5 = 1.5
Our Final Answer!