In probability theory and statistics, the relative standard deviation (RSD or %RSD) is the absolute value of the coefficient of variation. It is often expressed as a percentage. A similar term that is sometimes used is the relative variance which is the square of the coefficient of variation.Dodge, Y. (2003) The Oxford Dictionary of statistical Terms, OUP. ISBN 0-19-920613-9 Also, the relative standard error is a measure of a statistical estimate's reliability obtained by dividing the standard error by the estimate; then multiplied by 100 to be expressed as a percentage.
The relative standard deviation is widely used in analytical chemistry to express the precision and repeatability of an assay.
100 × = relative standard deviation expressed as a percentage