the deviation of a measurement result from the true value of the quantity being measured. A distinction is made between systematic errors, random errors, and blunders (also called gross errors, or mistakes).
Systematic errors result chiefly from measuring-device errors and the imperfection of measurement techniques. Random errors are due to a number of uncontrolled circumstances, for example, small variations in the conditions of measurement. The causes of blunders include disrepair of measuring devices, misreading of instruments, and drastic changes in the conditions of measurement. Blunders are usually disregarded when results are processed. The effect of systematic errors can be reduced by introducing corrections or by multiplying the instrument readings by correction factors. Estimates of random errors are obtained by the methods of mathematical statistics.