Anxiety can often make these related conditions worse, so talk with a mental health care professional if anxiety begins to interfere on a daily basis.
In probability theory and statistics, the variance of a random variable is a measure of its statistical dispersion, indicating how far from the expected value its values typically are. The variance of a real-valued random variable is its second central moment, and it also happens to be its second cumulant.
For a single variate having a distribution with known population mean , the population variance , commonly also written , is defined as. (1) where is the population mean and denotes the expectation value of . For a discrete distribution with possible values of , the population variance is therefore. (2) whereas for a continuous distribution, it is given by. (3) The variance is therefore equal to the second central moment .