When means and standard deviations are an incomplete summary of a continuous variable: problems, solutions, and utilising the reference ranges to check normality

In many areas of quantitative research, particularly in clinical research, it is common practice for continuous data (eg, personal information such as height, chemical levels in the body, or questionnaire total scores) to be summarised by the mean and standard deviation (SD). When using skewed continuous data, while still having merit, these summary measures should not be presented as the sole measures available. We argue that the reporting of median and interquartile interval for skewed data should be the predominant choice of summary measure, while the mean or SD can be presented as an additional measure. We also highlight how calculating a 95% reference range using the mean and SD can assess normality when the raw data are unavailable, for example, when reviewing a published article. We illustrate these concepts through examples and provide some practical guidance for authors and reviewers. The concepts discussed in this article highlight not only frequent author oversights when summarising data values, but how researchers, peer reviewers, and students can use the presented information to assess normality as a critical appraisal tool.