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### Stem and Leaf and Scatter Plots

```
Date: 10/13/98 at 23:01:44
From: Kyle Curre
Subject: Scatter plots and stem and leaf plot graphs

Hi. I am desperately trying to find out what stem and leaf and
scatter plots are. I have searched everywhere for an explanation of
what they are and how to make them. I am doing a math project for
Pre-Algebra, and I have to use stem and leaf and scatter plots. My
teacher wants us to be resourceful and find out all the information
we need ourself.

Thanks again,
Kyle Curre
```

```
Date: 10/14/98 at 09:20:13
From: Doctor Statman
Subject: Re: Scatter plots and stem and leaf plot graphs

Dear Kyle,

A stemplot is a graphical display that is used to represent one column
of data. A scatterplot represents the relation between two columns.

Here are two examples. Suppose I had one column of data that contained
the following numbers:

10 11 15 26 28 28 29 31 31 32 37 38

Look at the number 10, and think about it as a stem (1) plus a leaf
(0). So 10 becomes 1 | 0, writing the stem, then a bar, then the leaf.
Look at the 11. The 11 becomes 1 | 1, with the same stem as the 10.
So you can think of the 10 and the 11 as two leaves on the same stem
like this:

1 | 01

Now I'll put the rest of the stems and leaves for these numbers
together:

1 | 015
2 | 6889
3 | 11278

Can you see the stems for the 10's, 20's, and 30's? Can you see how
many 28's are in the data? Do you see how to break the numbers up into
stems and leaves?  Pretty cool, right?

Now a scatterplot is different - you need two columns of data.
Here are the heights and weights of the people in my family:

Height     Weight
(inches)   (pounds)
Mom         65        125
Kid 1       50         55
Kid 2       43         45
Kid 3       38         33
Kid 4       27         24

I can plot these two columns against each other in a scatterplot. I
made this one in a computer package called Minitab.

Scatterplot

-
-
-
Weight   -
-
-
120+                                            + Mom
-
-
-
-
60+                             +
-                      +
-                 +
-      +
-
--------+---------+---------+---------+---------+--------
Height      30        40        50        60        70

Do you see how there are six people in my family and six points (+) on
the scatterplot? Each plus sign is one person - I find their height on
the horizontal or x axis, and then I find their weight on the vertical
or y axis, and I put a + sign where they meet.

If you need more help, I suggest you visit a site like this one by Rex
Boggs called Exploring Data, from Queensland, Australia:

http://exploringdata.cqu.edu.au/

It has some good stuff about stemplots and scatterplots.

I hope this helps. Good luck with your project.

Statistically yours,

- Doctor Statman, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Statistics
Middle School Statistics

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