function variance = chi_variance ( a, b, c )

%*****************************************************************************80
%
%% chi_variance() returns the variance of the Chi PDF.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    06 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real A, B, C, the parameters of the PDF.
%    0 < B,
%    0 < C.
%
%  Output:
%
%    real VARIANCE, the variance of the PDF.
%
  variance = b * b * ( c - 2.0 * ( gamma ( 0.5 * ( c + 1.0 ) ) / gamma ( 0.5 * c ) )^2 );

  return
end
