Describing and estimating: use and abuse of standard deviations and standard errors.

Summarizing data using means and standard deviations (SDs) is commonplace in research reports. Many papers also present means and standard errors (SEs). Published reports are frequently confusing and inconsistent in their use of SDs and SEs. This short article clarifies the meaning and appropriate roles for these two important measures. The SD is used when describing study subjects and the SE is used when estimating the precision with which findings from the study sample can be extrapolated to other groups.