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Graphs for numerical variables.
One variable, listed as raw data, can be
visually displayed by a dot plot if the sample size is small
or a histogram if the sample size is large.
First let's make a dot plot.
If we're using just one
variable we can go to the graph menu,
dot plot,
one Y simple.
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When we click ok, we can then enter our variable of interest.
We'll look at C4 discrete.
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Next let's make a histogram.
Back in the graph
menu, histogram.
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If we're looking at just one variable, simple is
what we want to choose.
Then we can enter the variable of interest.
Let's look at discrete again.
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An alternative graph
is a box plot. It shows any outliers
in the data.
To make a box plot of discrete, we'll go
to graph, box plot,
one Y simple,
since we're still just looking at one variable.
Then we'll enter the graph variable
discrete.
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Two
variables as raw data can be organized into dot plots
and box plots using the same scale.
How you enter the commands in Minitab
depends on how the data is organized. Either the variables
are in two separate columns like
continuous one and continuous two,
in C5 and C6 or the data can
be in one column, like discrete, and then
there's another column of binary data that separates it into
two groups, like nominal binary in C1.
Let's first
make a dot plot of the continuous one and the continuous two
data.
We'll go back to graph, dot plot.
This time
we're dealing with multiple Y since we have two columns of data.
We can choose simple.
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Then all we need to do is enter both variables.
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Notice that the same scale is used for both
variables.
Let's create a box plot using the same variables.
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Back in the graph menu we'll select box plot.
Since we're dealing with
two columns we want multiple Y's simple.
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Once again I will enter both variables.
And we will see the graph on the same scale.
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If the two variables are one column of numbers and one column
of groups, and we want to create a dot plot or
a box plot on the same scale, we'll go back
into the graph menu. First, let's look at the dot plot.
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This time we want one Y
with groups, since we have one column of
numerical data and one column of a binary grouping data.
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Graph variables is going to be the column of numbers.
We'll use discrete.
Then under categorical variables we need to enter the
binary variable that breaks it up into groups.
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Here the same scale is used for both groups.
Let's look
at a box plot.
Back in the graph menu for box plot.
Since we have one column of numerical data we want one Y,
but we also have a column of groups.
So choose one Y with groups.
Let's look
at the continuous two data as our one column of numbers.
And we'll break it up into groups using nominal
binary.
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So there's one scale, but two
graphs.
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When looking at two
discrete or continuous variables at the same, like
before and after, we can create a scatter plot.
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This can be found in the graph menu under scatter plot.
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We can choose simple or with regression if
we'd like a regression line. First, let's look at simple.
Enter the Y variable
and the X variable
and hit ok.
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