Box Plot Tutorial

Table of Contents:

Constructing a Basic Box Plot (Single Box) ………………..…. Pages 2-8

Constructing a Complex Box Plot (Multiple Boxes) ……….… Pages 9-11

Making a More “Professional” Box Plot ……………………. Pages 12-15

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A. BASIC BOX-PLOT INSTRUCTIONS (SINGLE BOX)

A box-plot allows us to look at the distribution of data. By looking at a box-plot you can determine how "spread-out" the data is, where the data is centered, and make some quick assumptions about outliers and significant differences between data sets. For this exercise, you will be making one box-plot of data.

1. Type your data into one column.

 

2. Type Q1, Min, Median, Max, and Q3 into a new column. They MUST be in this order.

 

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3. Determine the "First Quartile" by using an Excel Function. Type "=QUARTILE(first cell:last cell, 1)". First cell refers to the first cell that has data in it (i.e. A2), last cell refers to the last cell that has data in it (i.e. A13).

 4. Determine the "Minimum" value by using an Excel Function. Type "=MIN(first cell:last cell)". Or

you could sort the data or just try to find the smallest value by looking. The Excel Function is the easiest way, though.

 

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5. Determine the "Median" value by using an Excel Function. Type "=MEDIAN(first cell:last cell)".

 6. Determine the "Maximum" value by using an Excel Function. Type

"=MAX(first cell:last cell)". Or you could sort the data or just try to find the largest value by looking. The Excel Function is the easiest way, though.

 

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7. Determine the "Third Quartile" by using an Excel Function. Type "=QUARTILE(first cell:last cell,3)".

 8. Highlight the Table of Values (both the labels and the numbers).

 9. Go to "Insert" and Select "Chart". Insert a Line Chart. Then hit "Next".

 

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10. Select Series in "Rows". Then hit "Next".

 11. Insert an appropriate Title. Also insert a label for the y-axis. Then hit "Finish". Please note: When

you are making official figures, then you should not insert a chart title. Your title will be made later when you paste your chart in a Word document. You'll then put your figure title and caption under your chart.

 12. Double-click on the data so that a "Format Data Series" box comes up. Choose the "Options" Menu

from this box.

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13. Select "High-low lines" and "Up-down bars". Then hit "OK"

 14. Double-click on the white box. A box that says "Format Up Bars" should appear. Choose "Custom"

Border. Increase the "Weight" of the line so that it is thicker. Also choose "None" on the Area section. This will make the box clear. Then hit "OK".

 

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15. Double-click on the line that connects all the points. A box that says "Format High-Low Lines" should appear. Select "Custom" line and make the "Weight" thicker.

 16. You now have a basic box-plot of your data. You could go further with the formatting of your table

and make the points easier to see by clicking on them and making them thicker, etc. That is up to you. As long as you can see your median, your quartile lines, and your maximum and minimum, then you are ok.

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B. BOX PLOT INSTRUCTIONS (MULTIPLE BOXES)

1. Highlight the data that you want to graph.

 2. Go to "Insert" and select "Chart"

 3. Choose a "Line" Chart and then hit "Next".

 4. Make sure that you have data "in rows". Hit "Next".

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5. Select the "Title" tab and give labels to your axes. DO NOT PUT A TITLE. Your title will be put in later when you paste your charts into a Word Document.

 6. Select the "Legend" tab and uncheck "Show legend". You DON'T want a legend. Hit "Next".

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7. Place your chart as a "New Sheet". Give it a name by typing in the white box. Hit "Finish".

 

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8. Double-click on each line to get rid of it. When you double click on the connecting lines, a box will come up. Select "NONE" under "Patterns" and "Line". Do this for all the lines.

 9. Double-click on a datapoint so that the following box comes up. Select the "Options" tab and check

High-Low lines and Up-Down bars

 10. Your final product should look something like this. Now, there are several things that you can do to

make your graph more professional. These are listed in Section C.

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C. MAKING A MORE "PROFESSIONAL" BOX PLOT

1. Suppose you want to change the appearance of the data points that appear on the chart. Double-click on a data point. You should get a menu that allows you to modify the appearance of the points.

 2. Go to "Style" and select the straight line option.

 3. Go to "Foreground Color" and make the point black.

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 4. Repeat steps 1-3 for all the Maximum and Minimum Points. Also do the same for the medians. For

the Q1 and Q3 marks, make them so that there is no marker.

 5. Suppose you want to make the background white. Double-click on the background and choose "None"

under "Area".

 

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6. Suppose you want to make the lines that cross the chart a little lighter so that the boxes show up nicer. You can make the grid-lines gray by double-clicking on them. Then you select a gray under the color.

<> 7. Suppose you want to change the scale of your axes. Double-click on the axis and select "Scale". Then

unclick the box under "Automatic" for the min and max. Put in your own numbers for what you want. Remember, all your charts should probably have the same scale so that they can easily be compared to each other.

 

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8. Suppose you want to change the axis title. Or maybe you want to make it a larger or different font. You should double-click on it and modify it how you want.

 9. When you are all done, you should have a very professional-looking, clean chart. Remember, you can

modify little things like the font style of the axes, how thick the lines are, the scales, etc. until you get the kind of graph that you are looking for.

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