About: Q-function

In statistics, the Q-function is the tail distribution function of the standard normal distribution. In other words, is the probability that a normal (Gaussian) random variable will obtain a value larger than standard deviations. Equivalently, is the probability that a standard normal random variable takes a value larger than . If is a Gaussian random variable with mean and variance , then is standard normal and where . Other definitions of the Q-function, all of which are simple transformations of the normal cumulative distribution function, are also used occasionally.