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The night before class, get two pitchers. Label one
pitcher A and the other one B. Pour plain water in pitcher
A. In pitcher
B, put a few of clear liquid soap fill it with water.
This needs to be done the night before so that the soap bubbles
have
a chance
to disappear and the solutions look the same.
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Review the
five key data points of a box-and-whisker plot: median, lower
extreme, upper extreme, lower quartile and
upper quartile.
-
Have students work with a partner. Each
pair needs an eye dropper or a pipette, a paper towel, two pennies,
two cups
and the Penny
Drop handout.
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Have the class read the scenario on the
handout.
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Instruct the students to label one of their cups “A” and
the other “B.” Then they should get a few
drops of each solution from the corresponding pitchers.
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The
students should then place a penny on the paper towel
and drop as many drops of the solution onto the penny
until it overflows.
They should record the number of drops (counting the
one when it overflowed). It’s important to have
as few variables as possible, so you will need to talk
about how far from the
penny they should drop the solution, whether to use
the head or the tail side, etc. One partner drops and
the
other records,
and then they switch jobs.
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After the students are finished,
you can go around the room and have them tell how many
drops they had for A
and for
B. They
should record this on their handout.
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Instruct the class
to find the median. They will need to put the number of drops
in order. Review their answers
to
make sure
they are correct before continuing.
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On the handout,
have the students make a number line using the lowest and the
highest points from either
A or B.
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Do these next steps for Solution A as a
class.
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Once the numbers are in order, the students need
to find the median of A. The best way to do
this is to
divide
the number
by two and count down from the top and draw
a line. Then count up from the bottom and draw a line.
The line will
either be between
two numbers, which means that you will have
to find the mean of those two numbers, or above
and below
a number,
meaning
that number is the median.
-
Instruct the students
to find the lower and upper quartiles and the two extremes
and record
these
on the handout.
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Have the students create the
box-and-whisker plot for Solution A.
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Be sure they label the
plot and put a title above the line.
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Once they have done this,
students will then make a box-and-whisker plot for
solution B on their
own.
-
Once the plots have been made,
you can ask several questions to the class.
Were the medians
for Solutions A and B the same?
What percent of the data
is in the box?
What percent of the data
is in each whisker?
Based
on their plots, are the solutions the
same?
- Have the students write
a few sentences about why they think the solutions
are or are not
the same.
