David W. Allan is an American atomic clock physicist and author of the Allan variance, also known as two-sample variance, a measure of frequency stability in clocks, oscillators and other applications.
David W. Allan (born 25 September 1936) is a world-renowned atomic clock physicist, most famous for the Allan Variance (AVAR), also known as two-sample variance. It is a measure of frequency stability in clocks, oscillators and is used in many other applications.