A power mean is a mean of the form M_p(a_1, a_2, ..., a_n) congruent (1/n sum_(k = 1)^n a_k^p)^(1/p), where the parameter p is an affinely extended real number and all a_k>=0. A power mean is also known as a generalized mean, Hölder mean, mean of degree (or order or power) p, or power mean.