A genetic test examines the genetic information contained inside a person's cells, called DNA, to determine if that person has or will develop a certain disease or could pass a disease to his or her offspring.
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.
The difference between the means of two samples, A and B, both randomly drawn from the same normally distributed source population, belongs to a normally distributed sampling distribution whose overall mean is equal to zero and whose standard deviation (standard error) is equal to. b = the size of sample B. To calculate the standard error of any particular sampling distribution of sample-mean differences, enter the mean and standard deviation (sd) of the source population, along with the values of n a and n b, and then click the Calculate button. Â©Richard Lowry 2001- All rights reserved.