Marcum Q-function

Marcum Q-function

In statistics, the Marcum-Q-function QM is defined as

Q_M (a,b) = \int_{b}^{\infty} x \left( \frac{x}{a}\right)^{M-1} \exp \left( -\frac{x^2 + a^2}{2} \right) I_{M-1} \left( a x \right) dx

QM is also defined as

Q_M (a,b) = \exp \left( -\frac{a^2 + b^2}{2} \right) \sum_{k=1-M}^{\infty} \left( \frac{a}{b}\right)^{k}  I_{k} \left( a b \right)

with modified Bessel function IM − 1 of order M − 1. The Marcum Q-function is used for example as a cumulative distribution function for noncentral chi-squared and Rice distributions.


References

  • Marcum, J. I. (1950) "Table of Q Functions". U.S. Air Force RAND Research Memorandum M-339. Santa Monica, CA: Rand Corporation, Jan. 1, 1950.
  • Nuttall, Albert H. (1975): Some Integrals Involving the QM Function, IEEE Transactions on Information Theory, 21(1), 95-96, ISSN 0018-9448
  • Weisstein, Eric W. Marcum Q-Function. From MathWorld—A Wolfram Web Resource. [1]