Standard error of measurement

The standard deviation (SD) represents the variation of the variable value, while the standard error (SEM) of the average value represents the distribution of the average value of the sample value, if you keep sampling. So SEM lets you know the accuracy of the average, and SD lets you know the variability of individual observations. They are related: SEM = SD/ (square root of sample size).

Simply speaking, it is the sampling error of the average, which reflects the sampling accuracy of the average. In China, the standard deviation SD is often used, SEM=SD divided by (the square root of the sample number). ...