1. 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”.www.ux1.eiu.edu/~cfgab 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. 2- Determine the mean and standard deviation for the remaining rows (this is explained on the same website under “Bio1100Excel- mean-standarddeviation”. Select the area in blue above and make graph by clicking on Chartwizard. 3- Now retype your mean and standard deviation values below the original table, then use the latter data to prepare a graph.

3. 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…

4. 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.

5. 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).

6. 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.

7. 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. Not a bad graph…