Important examples include the sample variance and sample standard deviation. This method corrects the bias in the estimation of the population variance. The Allan variance and Allan deviation describe frequency stability. Commonly used estimators include sample mean, unbiased sample variance and sample covariance. This has to be further divided by the standard deviation to get unit variance. Operators are also involved in probability theory, such as expectation, variance, and covariance. Part of the variance in estimates arises from differences in diagnostic criteria. This results in a volatility loss proportional to the market variance. Sometimes an assumption of finite variance formula 6 is not necessary. For example, a validity coefficient of .30 corresponds to 9 percent of variance explained. This assumption determines the form for the variance of . It is a weighted average of the variance. Now we face the problem of estimating the population variance. This is consistent with a calculated magnetic variance at this location in the early 1960s. Among those the total variance and Theo variance estimators should be considered.