### Making Graphs in Excel

###

### Making/Changing a Graph

- Select all the cells that contain the
data that you want to graph.
- Click on the Chart Wizard icon. You
will see a series of dialog boxes.
- Screen 1: Choose "XY
(Scatter)" and click "Next."
- Screen 2: This screen allows
you to choose which data to plot. Since you did
this before starting the Wizard, just click
"Next."
- Screen 3: This screen has
multiple menus. Play with the settings to see
what they do. Make sure your final graph has a
title, axes that are labeled (with units), and no
legend. When you are done, click "Next"
- Screen 4: This screen selects where you
will store the graph. Choose "As object in" to store the
graph in the same worksheet as the data and click"Finish"

- Once the graph is made, you can modify
most features of the graph by double-clicking on the
feature you want to change. You can also right-click on a
feature to get a menu. Try changing the color of the plot
area, the numbers on the axes and the appearance of the
data points.

### 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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