def approxChiFunction(dim):
 dim = float(dim)
 return (sqrt(dim) * ((1 - (1 / (4 * dim))) + (1 / (21 * (dim ** 2)))))

def approxChiFunction ( dim ) : dim = float ( dim ) return ( sqrt ( dim ) * ( ( 1 - ( 1 / ( 4 * dim ) ) ) + ( 1 / ( 21 * ( dim ** 2 ) ) ) ) )
returns chi approximation according to: ostermeier 1997 .