Mean, standard deviation, and SEM
Mean, sample SD, and SEM summarize different properties and must be labeled explicitly in text, tables, and error bars.
Mean describes center
The arithmetic mean is the sum divided by the observation count. It can be sensitive to outliers and may not represent a skewed distribution well.
Sample SD describes spread
Sample standard deviation commonly uses n − 1 when estimating population variability from a sample.
SEM describes estimated mean precision
SEM equals sample SD divided by the square root of n. It decreases with larger sample size and is not the spread of individual observations.
Label every summary
State n and identify whether error bars show SD, SEM, confidence intervals, or something else. Consistent symbols without definitions remain ambiguous.
Sources and boundaries
Solice develops LabCrux. The independent sources above do not sponsor or endorse the product. This page explains a review method; your experimental evidence, course instructions, and instructor remain authoritative.