In 41 patients, all hyperfunctioning parathyroid tissue was resected at the time of surgery and confirmed by a corresponding decrease in the intraoperative postexcision rapid PTH determination as well as by subsequent normalization of postoperative serum calcium and PTH levels and resolution of clinical symptoms.
In other words, the standard deviation Ï (sigma) is the square root of the variance of X; i.e., it is the square root of the average value of (X â Î¼) 2. The standard deviation of a (univariate) probability distribution is the same as that of a random variable having that distribution.
Variance is non-negative because the squares are positive or zero. The variance of a constant random variable is zero, and if the variance of a variable in a data set is 0, then all the entries have the same value. Variance is invariant with respect to changes in a location parameter.That is, if a constant is added to all values of the variable, the variance is unchanged.ere Cov(â, â) is the covariance, which is zero for independent random variables (if it exists). The formula states that the variance of a sum is equal to the sum of all elements in the covariance matrix of the components.