Download Excel-graph

Graphing with error bars
using Microsoft Excel
1. Enter data and prepare a graph as described in “Excel-simple
graph” found by visiting www.ux1.eiu.edu/~cfgab then
clicking on “Link to courses”.
For this demonstration, we shall use some class measurements
of Daphnia heart rate upon exposure to alcohol.
The mean and standard deviation are determined using the formula
“=AVERAGE(C3:P3)” and “=STDEV(C3:P3)”, respectively.
I also formatted columns Q and R to give only one decimal place.
2- Determine the mean and standard deviation for the remaining
rows (this is explained on the same website under “Bio1100Excelmean-standarddeviation”.
3- Now retype your mean and standard deviation values below the
original table, then use the latter data to prepare a graph.
Select the area in blue above and make graph by clicking on
Chartwizard.
Now your graph should something look like this:
4. To apply error bars, left click
on any data point and select
“Format Data Series..” then…
5- Select the
“Y Error
bars” tab,
“Both”,
and“Custom”
6. Select this icon. This window below will appear. Now highlight the three
standard deviation values and press Enter. This screen will reappear. Select this icon.
Now again highlight the standard deviation values and press Enter.
Now your graph should have error bars.
Note that the graph appears very different because the degree of error is very
large in this set of data. While the data original graph appeared to suggest an
effect of alcohol on heartbeat rate, the grouped data shows no significant effect.
However, your individual data from multiple trials would likely show a
significant effect due to alcohol treatment. Why is this? Try graphing your own
multiple data points (see next page).
Here is a
graph from
data from an
individual pair
of students.
This graph looks bad, so right click on
the Y axis, select “Format axis”, then
enter these minimum and maximum
values. The enter the std dev error bars
as before. The graph is shown on the
next page.
Not a bad graph…
But this graph might look
better as a bar graph
without a trend line.
Simply right click on chart,
select “chart type” and
choose “column”. Also,
select and delete the
trendline.