Graphing with error bars

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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(C3P3) and
STDEV(C3P3), respectively.
I also formatted columns Q and R to give only one
decimal place.
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2- Determine the mean and standard deviation for
the remaining rows (this is explained on the
same website under Bio1100Excel-mean-standarddevi
ation.
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.
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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
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5- Select the Y Error bars tab, Both,
andCustom
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.
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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).
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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.
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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.