Saturday, January 9, 2016

STEP by STEP on How to Create Error Bars in a Graph by Using Microsoft Excel 2013

As a Science postgraduate student, we often encounter the following question from our supervisor, “Where is the error bar in your graph?” Error bars are a graphical representation of the variability of data and are used on graphs to indicate the error, or uncertainty in a reported measurement [1].Error bar is important especially to represent your findings in an article, for example:


Adapted by permission from Macmillan Publishers Ltd: [NATURE] (Dalladay-Simpson, P., Howie, R. T., & Gregoryanz, E. (2016). Evidence for a new phase of dense hydrogen  above 325 gigapascals. Nature, 529(7584), 63-67. doi: 10.1038/nature16164


The values of Time (min) and Average Temperature (ᴼC) for the following example were taken from this video. Time (min) is independent variable (IDV) while Average Temperature (ᴼC) is dependent variable (DV). The following Step By Step creating error bar in graph was done by Microsoft Excel 2013 (the steps may vary for different version of Microsoft Excel)

Average values were calculated by =AVERAGE(XX:XX) formula:



Standard deviation values were calculated by the following formula: =STDEV(XX:XX):












Highlight the values in the Time (min) column:


Now while hitting CTRL tab continuously, highlight Average Temperature (ᴼC) values: 



Release the CTRL tab after two columns - Time (min) and Average Temperature (ᴼC) are highlighted:



Click INSERT > CHART > Scatter. You will see your scatter graph created:



Next. Click Design > Error Bar > More Error Bars Options…:



ERROR BAR option on the bottom left of your excel sheet. Scroll down by using the far left tab (as in green circle), and check Custom and click Specify Value (red rectangle):




When Custom Error Bar box pop up, delete “={1}” in Positive Error Value and Negative Error Value by using <-BACK SPACE tab:



Now, click on the small icon (as shown by red arrow) :




After that, highlight S.D. values, and click on icon (as shown by red arrow):




Repeat the same procedure for Negative Error Value, and hit OK:




Next, click on one of the HORIZONTAL error bar in the graph (as shown by red arrow):

:






 Then, in the Format Error Bars > Error Amount> check Fixed value and enter “0”:




 Close the Format Error Bars Box and Walla! You will get a vertical error bar in your graph:





ZOOM IN :








References:
2. https://youtu.be/2Etko-slowk
3. Dalladay-Simpson, P., Howie, R. T., & Gregoryanz, E. (2016). Evidence for a new phase of dense hydrogen  above 325 gigapascals. Nature, 529(7584), 63-67. doi: 10.1038/nature16164

Prepared by,
M. Sc. (Last updated: 09.01.2016)

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