Making Graphs in Excel


Making/Changing a Graph

Adding Error Bars

Right-click on a data point and choose "Format data series..." Click on the "Y error bars" tab. Choose "Both" under "Display" and "Fixed Value" under "Error Amount". Then enter the uncertainty for the y-values in the box marked "Fixed Value."

Adding a Trendline

Sometimes you want to find (and interpret) the equation that relates the two variables you graphed. To make a trendline and determine its equation, right-click on a data point and choose "Add trendline." Choose the shape that best describes your graph. Click on the "Options" tab. Check the box for "Display equation on chart" Use the simplest equation that you think will cut through all the error bars on your graph. You may need to try a couple of trendlines before you get the most appopriate one. To clear a trendline, right-click on the trendline and select "Clear".

Warning: It is very easy to use the trendline tools to produce nonsense. The purpose of his tool is to find the simplest mathematical model that explains the relationship between the two variables you are graphing. Look at the equation and shape of the trendline critically: Do they make sense? Is this the simplest possible explanation for the relationship between the two variables?


Copy Data and Graphs into a Word Document

You can copy graphs and data from Excel to Word. Just select the graph (or cells) and use the Ctrl-C and Ctrl-V shortcuts to copy and paste.

Sample Data

The sample data below is from a lab on DC circuits. The student was trying to determine how the resistance (R) of a wire depends on its length (L).

Length (cm) Resistance (Ohms)
1.0 12.1
2.0 21.3
3.0 30.2
4.0 39.2
5.0 48.8

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