Introduction
Today I would like to focus on the confusing reporting of findings using mean +/- error bars. There is a very heterogeneous use of error bars in publications.
– Some are unlabeled (yes this occurs quite often unfortunately even in 2024). The articles with incomplete legends represent both the biological and physical sciences, across many different disciplines, and clearly should not be considered isolated examples.
– Some are used in a descriptive manner: range shows the spread of the data, SD quantifies the variability in the data around the mean
– Some are used for inferential purposes (classic SE, robust SE, CI, etc.)
It can be quite confusing.
4 Basic Rules for Reporting Error Bars
When reporting error bars in studies, several common errors can occur. These errors can mislead readers and obscure the true meaning of the data.
Here are some basic rules to follow:
Rule 1️⃣: when showing error bars, always describe in the figure legends what they are.
Rule 2️⃣: the value of n (i.e., the sample size, or the number of independently performed experiments) must be stated in the figure legend.
Rule 3️⃣: error bars and statistics should only be shown for independently repeated experiments (true replicates), and never for replicates.
Rule 4️⃣: because experimental investigators are usually trying to compare experimental results with controls, it is usually appropriate to show inferential error bars, such as SE or CI, rather than SD. However, if n is very small (for example n = 3), rather than showing error bars and statistics, it is better to simply plot the individual data points.
In general for inferential purposes, it is more appropriate to report CI than SE.
Conclusion
Accurate and clear reporting of error bars is essential for the proper interpretation of study results. By following best practices and avoiding common errors, researchers can effectively communicate the variability and precision of their data, enhancing the transparency and reliability of their findings.
Reference
Cumming G, Fidler F, Vaux DL. Error bars in experimental biology. J Cell Biol. 2007 Apr 9;177(1):7-11. doi: 10.1083/jcb.200611141. PMID: 17420288; PMCID: PMC2064100.
hashtag#errorbars hashtag#reporting hashtag#findings hashtag#science
“Error bars commonly appear in figures in publications, but experimental biologists are often unsure how they should be used and interpreted. In this article we illustrate some basic features of error bars and explain how they can help communicate data and assist correct interpretation. Error bars may show confidence intervals, standard errors, standard deviations, or other quantities. Different types of error bars give quite different information, and so figure legends must make clear what error bars represent. We suggest eight simple rules to assist with effective use and interpretation of error bars.”