2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/168564We investigate a two-parameter entropy introduced by Schwämmle and Tsallis and obtain its probability distribution in the canonical ensemble. The probability distribution is given in terms of the Lambert W-function which has been used in many branches of physics, especially in fractal structures. Also, extensivity of $S_{q,q'}$ is discussed and a relationship is found to exist between the probabilities of a composite system and its subsystems so that the two-parameter entropy, $S_{q,q'}$, is extensive.10 pagesStatistical Mechanicstext