Abstract
The median of a standard gamma distribution, as a function of its shape parameter k, has no known representation in terms of elementary functions. In this work we prove the tightest upper and lower bounds of the form 2−1/k(A + k): an upper bound with A = e−γ (with γ being the Euler–Mascheroni constant) and a lower bound with A = log ( 2 ) - 1 3. These bounds are valid over the entire domain of k > 0, staying between 48 and 55 percentile. We derive and prove several other new tight bounds in support of the proofs.
Publisher
Public Library of Science (PLoS)