📘 How to interpret a standard error
Standard error summarizes how a statistic wobbles across repeated samples — not how individual observations scatter around a mean.
3
lessons
~15 min
to learn
Adults
level
What you’ll learn
- Name spread versus precisionDistinguish standard deviation of data from standard error of an estimate.Standard deviation describes observations; standard error describes sampling variability of a statistic.
- How sample size shapes SECalculate the estimated SE of a mean and explain how repeated samples and sample size change precision.Estimated SE is s divided by square root of n; quadrupling n roughly halves the mean's SE when variability is stable.
- Read and check SEInterpret SE in original units, connect it to confidence intervals, and check design assumptions.An SE summarizes estimator precision, not individual spread; a small SE is not proof of validity.
Questions this course answers
What does a standard error describe?
A standard error is the standard deviation of a statistic's sampling distribution.
For a sample mean, what happens to estimated SE when n is multiplied by four and s stays similar?
The sample mean's estimated SE is s divided by square root of n.
An SE of 1.5 minutes for a mean waiting time is measured in what units?
The standard error has the same units as the statistic it describes.
What should you check before trusting a small SE?
A simple SE can be too small when the design or dependence is not handled correctly.
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