In mathematics, the root mean square of a set of values is the square root of the set's mean square. Given a set , its RMS is denoted as either or . The RMS is also known as the quadratic mean, a special case of the generalized mean. The RMS of a continuous function is denoted and can be defined in terms of an integral of the square of the function. In estimation theory, the root-mean-square deviation of an estimator measures how far the estimator strays from the data.