What Is Standard Error?
The standard error of the mean measures how much a sample mean is expected to vary from the true population mean because of random sampling. It is calculated as the sample standard deviation divided by the square root of the sample size: SE = s ÷ √n.
Standard Error vs. Standard Deviation
Standard deviation describes the spread of individual values; standard error describes the precision of the estimated mean. Larger samples produce smaller standard errors.
Example
With s = 10 and n = 25, SE = 10 ÷ 5 = 2.
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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.