Total variance, an estimator of long-term frequency stability

Total variance is a statistical tool developed for improved estimates of fr equency stability at averaging times up to one-half the test duration. As a descriptive statistic, total variance performs an exact decomposition of t he sample variance of the frequency residuals into components associated wi th increasing averaging times. As an estimator of Allan variance, total var iance has greater equivalent degrees of freedom and lesser mean square erro r than the standard unbiased estimator has.