The component of error that scatters around a mean when the same quantity is measured repeatedly under the same conditions, driven by electrical noise, small temperature swings, vibration and operator variation. Its spread is characterized by the standard deviation of repeated readings, and the scatter of an average shrinks with the square root of the number of readings. It cannot be corrected, only reduced by averaging or by quieter conditions.
Last digit is bouncing around, that's random error, take ten readings and average them.
Also heard as
- random effect
Related terms
Systematic error
Error component that pushes every repeat reading the same way, or follows a pattern you can predict and correct.
Repeatability
How tightly readings bunch when one person repeats a measurement with the same setup, in one place, in one short sitting.
Standard deviation
The usual measure of scatter in a set of values, the square root of the average squared deviation from the mean.
Type A evaluation
Putting a number on an uncertainty component by running statistics on your own repeat readings.