asa243, a FORTRAN90 code which computes the cumulative density function (CDF) of the noncentral Student's T probability density function, by Russell Lenth.

The code is Applied Statistics Algorithm 243.


The computer code and data files described and made available on this web page are distributed under the MIT license


asa243 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and Programs:

ASA005, a FORTRAN90 code which evaluates the CDF of the noncentral T distribution.

ASA076, a FORTRAN90 code which evaluates the Owen's T function, needed to compute the CDF of the noncentral T distribution.


owen, a FORTRAN90 code which evaluates Owen's T function.


Original FORTRAN77 version by Russell Lenth; FORTRAN90 version by John Burkardt.


  1. William Guenther,
    Evaluation of probabilities for the noncentral distributions and difference of two T-variables with a desk calculator,
    Journal of Statistical Computation and Simulation,
    Volume 6, Number 3-4, 1978, pages 199-206.
  2. Russell Lenth,
    Algorithm AS 243: Cumulative Distribution Function of the Non-Central T Distribution,
    Applied Statistics,
    Volume 38, Number 1, 1989, pages 185-189.

Source Code:

Last revised on 22 May 2020.