The signed difference between an observed value and its expected or reference value. A positive deviation means the reading is higher than the nominal target, while a negative deviation means it is lower. It forms the basis of calculating standard deviation and assessing instrument bias.
Heard on the job
The calibration report shows a deviation of +0.02 volts at the 10-volt test point.
Related terms
Error
The signed difference between a measured value and the reference value of the quantity being measured.
Standard deviation
The usual measure of scatter in a set of values, the square root of the average squared deviation from the mean.
Bias
The estimated systematic offset of a measuring system: its average reading minus the reference value.