title: Standard deviation and standard error of the mean.
abstract: In most clinical and experimental studies, the standard deviation (SD) and the estimated standard error of the mean (SEM) are used to present the characteristics of sample data and to explain statistical analysis results. However, some authors occasionally muddle the distinctive usage between the SD and SEM in medical literature. Because the process of calculating the SD and SEM includes different statistical inferences, each of them has its own meaning. SD is the dispersion of data in a normal distribution. In other words, SD indicates how accurately the mean represents sample data. However the meaning of SEM includes statistical inference based on the sampling distribution. SEM is the SD of the theoretical distribution of the sample means (the sampling distribution). While either SD or SEM can be applied to describe data and statistical results, one should be aware of reasonable methods with which to use SD and SEM. We aim to elucidate the distinctions between SD and SEM and to provide proper usage guidelines for both, which summarize data and describe statistical results.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Dong Kyu
authors.identifier: 0000-0002-4068-2363
authors.initials: DK
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Dongguk University Ilsan Medical Center, Goyang, Korea.
authors.forename: Junyong
authors.identifier: 0000-0001-7403-4287
authors.initials: J
authors.lastname: In
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Sangseok
authors.identifier: 0000-0001-7023-3668
authors.initials: S
authors.lastname: Lee
keywords: Standard deviation; Standard error of the mean