Adding Mean Values to a Scatterplot
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These directions assume you’ve already made a scatterplot with categories along the x-axis (go here for general directions).
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The following example is based on the butterfly data set which you can find here.
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Once you make and format your scatterplot, it should something look like this (for tips on formatting your graph, go here):
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To add mean values to a scatterplot, you need to setup two new columns in your data sheet, the first with the numbers representing your categories (in this case, 1, 2, and 3); the second with the corresponding mean values. You can calculate mean values using a calculator, formulas in Excel, or get them from statistical output from a t-Test or ANOVA.
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The two new columns in your spreadsheet should look like this:
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To add the mean values to your graph, right click within the graph and click Select Data. You should see a window that looks like this:
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Click Add, then type “mean values” for your Series name.
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Click in the Series X values box, and drag down your column of category values.
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Click in the Series Y values box (if you see “={1}”, delete it), then drag down your
column with your mean values.
Click OK. You should now see your mean values displayed on your graph something like this:
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In order to change the symbols on your graph, double click them so that you see a window like this:
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The most useful settings to change are Marker Options, Marker Fill, and Marker Line Color.
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If you’ll be printing out your graph, consider using colors that will work well when shown in black and white (or just use black or gray symbols).
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Here’s an example of symbols that will work for black and white printouts:
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It’s important that you either include a figure legend that shows what your symbols mean (as shown above), or explain your symbols in your figure description (as shown below).
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